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Equilibrium Problem - Left and right side and top and bottom side sum of any point are same in matrix

Problem Description :

#import <Foundation/Foundation.h>

int leftArraySum(NSMutableArray *A,int n)
    NSInteger sum  = 0;
    for(int i=0;i<n;i++)
        sum += [[A objectAtIndex:i] integerValue];   
    return sum;

int reightArraySum(NSMutableArray *A,int n)
     NSInteger sum  = 0;
    for(int i=n+1;i<[A count];i++)
        sum += [[A objectAtIndex:i] integerValue];   
    return sum;

int topArraySum(NSMutableArray *A,int n)
     NSInteger sum  = 0;
    for(int i=0;i<n;i++)
        sum += [[A objectAtIndex:i] integerValue];   
    return sum;

int bottomArraySum(NSMutableArray *A,int n)
     NSInteger sum  = 0;
    for(int i=n+1;i<[A count];i++)
        sum += [[A objectAtIndex:i] integerValue];   
    return sum;

int solution(NSMutableArray *A) {
    // write your code in Objective-C 2.0
    NSMutableArray *rowArr = [A objectAtIndex:0];
    int colCount = [rowArr count];
    int rowCount = [A count];
    NSMutableArray *arrRowSum = [[NSMutableArray alloc] initWithCapacity: rowCount];
    NSMutableArray *arrColSum = [[NSMutableArray alloc] initWithCapacity: colCount];
    for(int i=0;i<rowCount;i++)
        NSArray *colArr = [A objectAtIndex:i];
        NSNumber * sum = [colArr valueForKeyPath:@"@sum.self"];
        [arrRowSum insertObject:sum atIndex:i];
    for(int i=0;i<colCount;i++)
        NSInteger sum = 0;
        for(int j=0;j<rowCount;j++)
           sum +=  [[[A objectAtIndex:j] objectAtIndex:i] integerValue];
        NSNumber *sumVal = [NSNumber numberWithInt:sum];
        [arrColSum insertObject:sumVal atIndex:i];
    int result = 0;
    for (int i=1;i<rowCount;i++)
        int left = leftArraySum(arrRowSum,i);
        int right = reightArraySum(A,i);
        if(left  == right)
            for(int j=0;j<colCount;j++)
                int top = topArraySum(A,j);
                int bottom = bottomArraySum(A,j);
                   if(top == bottom )
                    result = i+j;
    return result;

What types of feature google map provide to developers?

Ans : 

Google map features :
  • Plotting places Near Me. Like near by hospitals, restaurants, temples
  • Direction ( route ), Distance, Travel time, Live traffic
  • Street view for 3D location
  • Geofencing
  • Live tracking location
  • Get current location
  • Put markers on various places
Alternatives of Google map api :
I am using MapMyIndia api due to high cost of Google map apis. I have also implemented here map. Both are nice.

There are two versions of here-map, free and premium. Premium here map service is better than free here map service. I have implemented live tracking of car, replay route, using both apis.

What are collection types in objective C and Swift?

Ans : 

In  iOS, there are 3 collection types

i. Array 
ii. Dictionary 
iii. Set.

There are two types of collection types. Mutable and Immutable. Mutable can be changed but immutable can not be changed once initialised.

Q. How to check nil keys in dictionary?
A. There is not any nil keys in dictionary.

Determine index of one integer in another integer - online programming question

Problem Description : Determine index of one integer in another integer

i.e If input A = 23,B = 1472367 then Output : 3 . Because '23' is 3rd index in '1472367'.

Asked in Company : Futurescape Technologies Pvt Ltd  via

Ans : 

#import <Foundation/Foundation.h>
// you can also use other imports, for example:
// #import <SomeLibrary/SomeFile.h>

// you can write to stdout for debugging purposes, e.g.
// printf("this is a debug message\n");

int solution(int A, int B) {
    // write your code in Objective-C 2.0
    NSString *strA = [NSString stringWithFormat:@"%d",A];
    NSString *strB = [NSString stringWithFormat:@"%d",B];
   NSRange range =   [strB rangeOfString:strA];
   if(range.location == NSNotFound)
   return -1;
   return range.location;

Do you like to use storyboard? Why? Can more than 1 storyboard allowed?

Ans : I like to use storyboard.

I am using storyboard due to advantage over XIB : See here

Yes, we can use more than 1 storyboard. We can make different storyboard for different features in same project.

Navigating from one storyboard to another storyboard :

1. Using segue :

  • Drag & Drop storyboard reference
  • Give name and assign viewcontroller (to which we want to navigate)
  • Give segue from viewcontroller to storyboard reference.
2. Using coding :

var anotherStoryboard = UIStoryboard(name: "another", bundle: nil)
var vc: UIViewController = anotherStoryboard.instantiateViewController(withIdentifier: "loginView")
present(vc, animated: false)

What is multiplier and ratio in auto layout in ios?

Ans :

Difference between Multiplier and Ratio : 

There is not any difference. Both are using for same purpose.

The Aspect Ratio is really just a convenient way to express the Multiplier when working in Interface Builder. It effectively gets "converted" to a multiplier.

You can confirm this while debugging by inspecting the constraint's .multiplier property. If you set a view's width to 60, and multiplier to 1:2 (resulting in an auto-layout height of 120), the actual value of .multiplier will be 0.5.

So, in my view, it depends on what feels more natural.

If I want a view to be 90% of the width of another view, I am much more likely to set the Multiplier to 0.9 --- which gives the exact same result as setting it to 9:10.

However, if I want a view to maintain an aspect ration of, say, 3-to-2, I am much more likely to set the Multiplier to 3:2 rather than 1.5.

Using a ratio can also be convenient when you have "non-simple" values. That is, it's easy to understand that a ratio of 3:2 is the same as 1.5. But what if I have an image with native size of 281 x 60, and I want to use those values to maintain ratio? 281:60 is easier to understand than .multiplier = 4.68333339691162.

And, while they are interchangeable, it is probably a bit more intuitive to use Ratio when constraining an object to itself - e.g. I want my view's width to be 2 x its own height, so 2:1 - and using Multiplier when constraining one object to another - e.g. I want my view's width to be 75% of the width of its superview, so 0.75.

Difference between nil, NIL and null

Ans : 

The difference is that while
NULL represents zero for any pointer,
nil is specific to objects (e.g., id) and
Nil is specific to class pointers.

Nil,Null and nil are used with below
1> Nil for Objective c Class
2> nil for Objective c object
3> Null for C pointer
1>Class A=Nil;
2>NSString strName=nil;
3>char *pointerChar = NULL;

OOPS Concept in iOS

Ans :  OOPS Concepts are mostly same in all language. Their working are same but conditions are different.

1.      Inheritance : It allows a class to be defined that has a certain set of characteristics(methods and variables) and then other classes to be created which are derived from that class. The derived class inherits all of the features of the parent class and typically then adds some features of its own.

2.      Encapsulation : That binds data and functions together and keeps both safe from outside interference and misuse. Data encapsulation’s benefit of data hiding.

Data encapsulation is a mechanism of bundling the data and the functions that use them.

Data abstraction is a mechanism of exposing only the interface and hiding the implementation details from the user.

3. Polymorphism : Difference process depends on type. The method to be invoked is determined at runtime based on the type of the object. It is like override and overload.

Override : Different class, same method name with signature. It is also called runtime or dynamic polymorphism.

Overload : Same class, method name same with Different parameter. It is also called compile-time or static polymorphism. 

‌Which method is called first when app start?

Ans :

According to apple doc,

  • (BOOL)application:(UIApplication *)application willFinishLaunchingWithOptions:(NSDictionary *)launchOptions{}
gets called before
  • (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions{}

Why array method containObject has id as parameter in ios?

Ans : id is a generic type. This means that the compiler will expect any object type there, and will not enforce restrictions. It can be useful if you're expecting to use more than one class of objects there. So you can add anything of type id to an NSArray.

So array method containObject has id type as parameter.

- (BOOL)containsObject:(ObjectType)anObject;

Usage :

bool bVal = [arr containObject:@5];

Difference between blocks and completion handler in iOS

Ans :


Blocks are a language-level feature added to C, Objective-C and C++, which allow you to create distinct segments of code that can be passed around to methods or functions as if they were values. Blocks are Objective-C objects, which means they can be added to collections like NSArray or NSDictionary.

They can be executed in a later time, and not when the code of the scope they have been implemented is being executed.
Their usage leads eventually to a much cleaner and tidier code writing, as they can be used instead of delegate methods, written just in one place and not spread to many files.
Syntax: ReturnType (^blockName)(Parameters)

see example:

int anInteger = 42;

void (^testBlock)(void) = ^{

    NSLog(@"Integer is: %i", anInteger);   // anInteger outside variables


// calling blocks like
Block with argument:

double (^multiplyTwoValues)(double, double) =

                          ^(double firstValue, double secondValue) {

                              return firstValue * secondValue;

// calling with parameter
double result = multiplyTwoValues(2,4);

NSLog(@"The result is %f", result);

Completion handler:
Whereas completion handler is a way (technique) for implementing callback functionality using blocks.
A completion handler is nothing more than a simple block declaration passed as a parameter to a method that needs to make a callback at a later time.
Note: completion handler should always be the last parameter in a method. A method can have as many arguments as you want, but always have the completion handler as the last argument in the parameters list.
- (void)beginTaskWithName:(NSString *)name completion:(void(^)(void))callback;
// calling
[self beginTaskWithName:@"MyTask" completion:^{
    NSLog(@"Task completed ..");
More example with UIKit classes methods.

[self presentViewController:viewController animated:YES completion:^{
        NSLog(@"xyz View Controller presented ..");
        // Other code related to view controller presentation...
[UIView animateWithDuration:0.5
                         // Animation-related code here...
                         [self.view setAlpha:0.5];
                     completion:^(BOOL finished) {
                         // Any completion handler related code here...
                         NSLog(@"Animation over..");

Why tableview cell separator leave some space before?

Ans : 

Alternatively, you can also edit this in interface builder (IB):
  1. Go to IB.
  2. Select Table View.
  3. Open "Attribute Inspector" on the right.
  4. Change "Separator Insets" from Default to Custom.
  5. Change the "Left" attribute from 15 to 0.
15 is default. So Left side space is seen before cell seperator.

Do you know SMTP? is it use SOAP or REST?

Ans : 

SMTP (Simple Mail Transfer Protocol) is a TCP/IP protocol used in sending and receiving e-mail.

SOAP and REST both allow you to create your own API. API stands for Application Programming Interface. It makes it possible to transfer data from an application to other applications. An API receives requests and sends back responses through internet protocols such as HTTP, SMTP, and others.

It use SOAP web-service. SOAP is protocol and rules are maintained by World wide web consortium(W3C).

Design such button in that text should be displayed below image

Ans : 

1) Select button and go to Attribute Inspector in your storyboard.

2) Assign Image to the button. (Don't use background Image)

3) Set Title text to that button.

4) Now you need to set edge and Inset so first select image from edge and set Inset as you need and then select title from edge and set inset as per your need.

Difference between viewdidload and viewwillappear?

Ans : 

ViewDidLoad - It is excecuted once. So writer settings like set label text in ViewDidLoad.
ViewWillAppear - It is called every time when view appear.

ViewDidLoad - It is called when view is begin constructed.
ViewWillAppear - When view is about ready to appear.

ViewDidLoad It is automatically called when view controller completely loaded into memory. Override this method to perform additional initialization on views that were loaded from xib.
I.e instance variable initialization, database access, network request
ViewWillAppear It is called when View is about to added on view hierachy. If we want to change some, then we have to override this method.Like change orientation, change screen data.

Suppose your tableview data will be changed periodically. Then you have to write [tableview reloaddata] in ViewWillApper.

Read UIViewController LifeCycle

What are join in sql? Explain Types of Join

Ans :

Join :
When we need data from more than 1 table, then we can fetch data from those table using joining those table. It will return only matching data from two tables.

Select * from table1 t1 inner join table2 t2 on t1.column1 = t2.column1

Types of Join :

1. Inner Join :
If we use inner join between two table, then only data exists in both table, are returned.

2. Outer Join :
    Left Outer Join : It returns all data from left table(table1) and only matching data from both table.
    Right Outer Join : It returns all data from right table(table2) and only matching data from both table.

3. Cross Join : It is like cartesian join. It returns all records from both table and it returns table1.count * table2.count records in returns. Suppose table1 has 4 records and table2 has 3 records and returns 4*3 records.

4. Self Join : If some column's reference has in same table then self join is used. It is same like inner join but here both left and right table are same. Its like if you table and Columns are such as MainID, Name, ParentID then you can make query like
Select * from table t1 join table t2 on t1.MainID = t2.ParentID

Difference between Strong and Weak in iOS

Ans : 

strong property means that you want to “own” the object. Only when you set the property to nil will the object be  destroyed. Unless one or more objects also have a strong reference to the object. This is the one you will use in most cases.
  1. Creates ownership between property and assigned value.
  1. This is default for object property in ARC so it does not let you worrying about reference count and release the reference automatically.
  1. It is replacement for retain. We use if and only if we need to use as retain.
  1. Retain count will be incremented.
  1. Creates non-ownerships between property and assigned value.
  1. Strong is used on parent object and weak is used on child object when parent is released then child object reference is also set to nil
  1. It helps to prevents retain cycles.
  1. It doesn’t protect the referenced object when collection by garbage collector.
  1. Weak is essentially assigned, un-retain property.
  1. Retain count will not be incremented.

Weak property means you don’t want to have control over the objects lifecycle. The object only lives on while another objects has a strong reference to it. If there are no strong references to the object then it will be destroyed. 
Weak reference is useful to avoid situation like retain cycle. Retain cycle occurs when two or more objects have strong reference to each other. This two object will never be freed in memory due to strong reference. So to avoid weak reference, One object has a strong ownership reference to another object, and another object should be have a weak reference to first object.

Strong references should be used when a parent object is referencing a child object and never the other way around. That is, a child class should not have a strong reference to the parent class.

Weak references should be used to avoid retain cycles and an object has the possibility to become nil at any point of it’s lifetime.

Good read : Click here

What are blocks in iOS?

Ans : 

Blocks are first-class functions, which is a fancy way of saying that Blocks are regular Objective-C objects. Since they’re objects, they can be passed as parameters, returned from methods and functions, and assigned to variables. A block creates a const copy of any local variable that is referenced inside of its scope.

Block is a chunk of code that can be executed at some future time.

Blocks can greatly simplify code. They can help you reduce code, reduce dependency on delegates, and write cleaner, more readable code.

Block is alternative of delegate or NSNotificationCenter. In delegate and NSNotificationCenter, callback methods and main method are written different places. So its more difficult to read. In block, call back method written in main method as parameter.

Declaration : return_type (^block_name)(param_type, param_type, ...)
int (^add)(int,int)

Definition : ^return_type(param_type param_name, param_type param_name, ...) { ... return return_type; }
^(int number1, int number2){ return number1+number2 }

Declaration + Definition : 

int (^add)(int,int) = ^(int number1, int number2){ return number1+number2; }

We can call block also like following : 

int resultFromBlock = add(2,2);

If we take example of NSArray using block :

[theArray enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop){

    NSLog(@"The object at index %d is %@",idx,obj);


If we take example of UIView animation using block :

[UIView animateWithDuration:5.0 
                        [animatingView setAlpha:0];
                        [animatingView setCenter:CGPointMake(, 
                     completion:^(BOOL finished) {
                         [animatingView removeFromSuperview];

Apple also suggest to use block instead of call back methods.

Difference between blocks and completion handler : 

We have understand what is block. Completion handler is a way (technique) for implementing callback functionality using blocks. As a completion handler parameter, we have to pass block.

Example of Completion handler is seen above as last example of blocks.

Completion handler always comes as last parameter.

Read more : Difference between blocks and completion handler

Expandable tableview Logic in iOS

Ans : 

Logic  : 

  • Display UITableView containing just the header/section titles for each category.
  • When a section is touched, expand it if it is not already expanded. Otherwise, collapse the section.
  • When a section is touched, expand it and if another section is currently expanded collapse that section so that only one section is expanded at a time.
  • To expand a section, determine the number of items that must be displayed within that section and insert that number of rows in the UITableView; then display the items in the newly inserted rows.
  • To collapse a section, determine the number of items currently displayed within that section and delete that number of rows from the UITableView.

To reload one section only : 

[self.tableView beginUpdates];
 (void)reloadSections:(NSIndexSet *)sections withRowAnimation:(UITableViewRowAnimation)animation:
[self.tableView endUpdates];

Difference between XIB and Storyboard

Ans : 


1) Xib files are used with a single UIView.

3)It's utilizes more memory as compared to storyboard and quiet slow.

4) It is compatible from iOS5 and onwards

5) You can do localizations for different languages and countries using different XIBs .

6) It's difficult to use same Xib to support multiple devices.

Storyboard :

1)You can layout all your Scenes like View Controllers, Nav Controllers, TabBar Controllers, etc in a single storyboard.

3)Usually fast and allocates less memory.

4)It's not compatible prior to iOS 5 .

5)"Dynamic" and "Prototype" cells can be used easily.

6)Storyboards best to use for the apps with a small to medium amount of screens.

Difference between synchronous and asynchronous calls in Objective-C

Ans : 

Synchronous :
This call means task will be executed in order.
Asynchronous : This call means task may or may not be executed in order.

When call is called synchronously, then thread that initiated that operation will be wait to current task to be finished.
When call is called asynchronously, then it will not wait.

If we want to do some task without harassing UI, we can do those tasks in background thread. This goal is to keep free main thread, so it continuously respond UI event. So we can dispatch our task in background state asynchronously.

So for do task in background thread, we will divide in 2 parts.

1. GCD - Grand Central Dispatch. By using GCD, you have to grab one of global background queue or create your own background queue.

// one of the global concurrent background queues
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

// or you could create your own serial background queue:
// dispatch_queue_t queue = dispatch_queue_create("", 0);

2. Dispatch your task to that queue asynchronously

dispatch_async(queue, ^{
    // task that to be done in background and it may be slow

The pattern for operation queues is very similar. Create an operation queue and add operations to that queue.

Lets see example :

Asynchronous call with Multithreading :

// Methods gets called in different thread and does not block the current thread.
[NSURLConnection sendAsynchronousRequest:request
    ^(NSURLResponse *response, NSData *data, NSError *error) {

Synchronous call with Multithreading (not so useful):

//Do something
dispatch_sync(queue, ^{
    //Do something else // work in another queue or thread

//Do some more task

Difference between thread-safe and non-thread-safe in iOS

Ans : 

Thread-Unsafe -> If any object allow to modify by more than one thread at the same time.  (non-atomic property is thread-unsafe. Comments are welcomed)

Thread-safe -> If any object not allow to modify by more than one thread at the same time.Immutable objects are generally thread-safe. (atomic property attribute type. Comments are  welcomed)

In general, immutable classes like NSArray, let are thread-safe, while their mutable variants like NSMutableArray,var are thread-unsafe.

Which type of encryption you have used in iOS App?

Ans : I have used trippleDES for passing data in request to server.

NSData *jsonData = [NSJSONSerialization dataWithJSONObject:dicPostDict options:kNilOptions error:&error];

 NSString *strJsonData=[[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];

 NSData *encryptedJsonString = [CommonMethods tripleDesEncryptString:strJsonData  key:@"2-055PL&okjnnhkey@inihgr" error:nil];
 NSString *strencryptedJsonString = [encryptedJsonString base64Encoding];

Access controls in Swift

Ans : 

Access controls
keyword enables you to hide the implementation details of your code, and to specify a preferred interface through which that code can be accessed and used.

Swift 3, Swift 4

There are 5 access controls.
1. open (most accessible, least restrictive)
2. public
3. internal (default)
4. fileprivate
5. private (least accessible, more restrictive)

1. open : It enable entity to be used in and outside of defining module and also other module. UIButton, UITableView is in UIKit. We import UIKit and make subclass of UITableView and use in our module in which we have imported UIKit. So tableview subclass of UITableView defined in UIKit is used in our module. Sot it is accessible in our module.

open class UITableView : UIScrollView, NSCoding { }

2. public : open allows us to subclass from another module. public allows us to subclass or override from within module in which it defined.

//module X
public func A(){}
open func B(){}

//module Y
override func A(){} // error
override func B(){} // success

So open class and class members can be accessible and overridden in which it is defined and also in which module it is imported.
public class and class members can be accessible and overridden only in which it is defined.

3. internal : Internal classes and members can be accessed anywhere within the same module(target) they are defined. You typically use internal-access when defining an app’s or a framework’s internal structure.

4. fileprivate : Restricts the use of an entity to its defining file. It is used to hide implementation details when details are used in entire file. fileprivate method is only accessible from that swift file in which it is defined.

5. private : Restricts the use of an entity to the enclosing declaration and to extension of that swift file or class. It is used to hide single block implementation. private entity can be accessible in swift 4 but it gives error in swift 3.

MVC in iOS

Ans : The main goal of MVC pattern is separate data/logic, view and controller. There are 3 layers.

1. Model : Models are representation of your app's data. There is user class or struct. So it has fields like name, birthdate, etc. It is data reside in Model layer.

2. View : It is object which user can see and interact with. UILabel showing text is one kind of view.

3. Controller : Controller mediates between Model and View. It takes data from model and show on views and also update model when user interacts with view.

File Structure :

MVC File Structure

Understand MVC using UITableView

Explain MVC through implementation of UITableView

Ans :

Read first about MVC

Let's understand to implement UITableview in MVC

1. We write fetching data query or request web-service and parse json,xml and save data to any global variable like dictionary, array, etc. So all inserting, fetching methods and data variable are comes under M.....Model

2. We make custom tableview cell, and put various types of views like UILabel, UITextField, UIButton for displaying in UITableView on screen. So this comes under V....View.

3. For displaying TableView, we will take UIVIewController or UITableviewController. This are responsible for various activity like telling how many section, rows are there, on delete button deleting row, how much height of cell, etc... So this comes under C....Controller.

Which delegate method called when I click on push notifications?

Ans : 
Different app delegate method called depends on following scenarios

For silent notification : 

App is in Foreground
No system alert shown
application:didReceiveRemoteNotification:fetchCompletionHandler: is called

App is in Background
System alert is shown
application:didReceiveRemoteNotification:fetchCompletionHandler: is called

App is in Suspended
App state changes to Background
System alert is shown
application:didReceiveRemoteNotification:fetchCompletionHandler: is called

App is Not Running because killed by user
System alert is shown
No callback is called

Normal Push Notification (no content-available) :

App is in Foreground
No system alert shown
application:didReceiveRemoteNotification:fetchCompletionHandler: is called

App is in Background or Suspended
System alert is shown
No method is called, but when user tap on the push and the app is opened
application:didReceiveRemoteNotification:fetchCompletionHandler: is called

App is in Not Running
System alert is shown
No method is called, but when user tap on the push and the app is opened
application:didFinishLaunchingWithOptions: then application:didReceiveRemoteNotification:fetchCompletionHandler: are both called

Add column in SQLite

Ans : 
If we have uploaded our app ver 1.0 and we want to add columns in sqlite database, then following thing can done.

If we have sqlite database which table structure can be changed after release. Then we need to maintain database version. We can update database version by excecuting query like PRAGMA user_version = version_num; (For swift : PRAGMA table_info(tblTest))

In second release If we need to add columns, then we can check database version, If database version is old version then we can execute following query :

ALTER TABLE {tableName} ADD COLUMN COLNew {type};

Query for last inserted row in SQL database


If column is primary key and integer, then ,

Sqlite : SELECT * FROM table ORDER BY column DESC LIMIT 1;




Last inserted id is : [fmdb lastInsertRowId];

Sqlite3 all functions : 

sqlite3_open: This function is used to create and open a database file. It accepts two parameters, where the first one is the database file name, and the second a handler to the database. If the file does not exist, then it creates it first and then it opens it, otherwise it just opens it.
sqlite3_prepare_v2: The purpose of this function is to get a SQL statement (a query) in string format, and convert it to an executable format recognisable by SQLite3.
sqlite3_step: This function actually executes a SQL statement (query) prepared with the previous function. It can be called just once for executable queries (insert, update, delete), or multiple times when retrieving data. It’s important to have in mind that it can’t be called prior to the sqlite3_preprare_v2 function.
sqlite3_column_count: This method’s name it makes it easy to understand what is about. It returns the total number of columns (fields) a contained in a table.
sqlite3_column_text: This method returns the contents of a column in text format, actually a C string (char *) value. It accepts two parameters: The first one is the query converted (compiled) to a SQLite statement, and the second one is the index of the column.
sqlite3_column_name: It returns the name of a column, and its parameters are the same to the previous function’s.
sqlite3_changes: It actually returns the number of the affected rows, after the execution of a query.
sqlite3_last_insert_rowid: It returns the last inserted row’s ID.
sqlite3_errmsg: It returns the description of a SQLite error.
sqlite3_finalize: It deletes a prepared statement from memory.

sqlite3_close: It closes an open database connection. It should be called after having finished any data exchange with the database, as it releases any reserved system resources.

UITableviewDelegate and UITableViewDataSource Methods

Ans : 

UITableview's Delegate Methods :

The UIViewController in which UITableView you use must adopt the UITableViewDelegate protocol. Optional methods of the protocol allow the delegate to manage selections, configure section headings and footers, help to delete and reorder cells, and perform other actions.

Configuring Rows for the Table View

- tableView:heightForRowAtIndexPath:
- tableView:indentationLevelForRowAtIndexPath:
- tableView:willDisplayCell:forRowAtIndexPath:

Managing Accessory Views

- tableView:accessoryButtonTappedForRowWithIndexPath:
- tableView:accessoryTypeForRowWithIndexPath: Deprecated in iOS 3.0

Managing Selections

- tableView:willSelectRowAtIndexPath:
- tableView:didSelectRowAtIndexPath:
- tableView:willDeselectRowAtIndexPath:
- tableView:didDeselectRowAtIndexPath:

Modifying the Header and Footer of Sections

- tableView:viewForHeaderInSection:
- tableView:viewForFooterInSection:
- tableView:heightForHeaderInSection:
- tableView:heightForFooterInSection:

Editing Table Rows

- tableView:willBeginEditingRowAtIndexPath:
- tableView:didEndEditingRowAtIndexPath:
- tableView:editingStyleForRowAtIndexPath:
- tableView:titleForDeleteConfirmationButtonForRowAtIndexPath:
- tableView:shouldIndentWhileEditingRowAtIndexPath:

Reordering Table Rows

- tableView:targetIndexPathForMoveFromRowAtIndexPath:toProposedIndexPath:

Copying and Pasting Row Content

- tableView:shouldShowMenuForRowAtIndexPath:
- tableView:canPerformAction:forRowAtIndexPath:withSender:
- tableView:performAction:forRowAtIndexPath:withSender: 

UITableview's Data Source Methods : The NSTableViewDataSource protocol declares the methods that an instance of NSTableView that provides the data to a table view and allows editing of the contents of its data source object.

All the methods are described in the following.

Getting Values

- numberOfRowsInTableView: (Required)
- numberOfSectionInTableView:
- cellForRowAtIndexPath : (Required)
- tableView:objectValueForTableColumn:row:

Setting Values

- tableView:setObjectValue:forTableColumn:row:

Implementing Pasteboard Support

- tableView:pasteboardWriterForRow:

Drag and Drop

- tableView:acceptDrop:row:dropOperation:
- tableView:namesOfPromisedFilesDroppedAtDestination:forDraggedRowsWithIndexes:
- tableView:validateDrop:proposedRow:proposedDropOperation:
- tableView:writeRowsWithIndexes:toPasteboard:
- tableView:draggingSession:willBeginAtPoint:forRowIndexes:
- tableView:updateDraggingItemsForDrag:
- tableView:draggingSession:endedAtPoint:operation:


- tableView:sortDescriptorsDidChange:

Tips : UITableViewDelegate has no any required methods.