Cocoa in iOS

Arrangement: While working on a application you may have used some predefined values. The visibility of these values can be application level, feature level or class level. For the  convenience  we give name to these values and then use in the application. In this case the name given by you only representing the single value and it never change to represent some other value thats why it is called Constant. On the other hand variables are like us doing jobs in IT World and can switch from one organization( value ) to other. Like while choosing a partner for marriage you may choose best for you by seeing multiple persons and still after sometime you feel stuck. Same may happen you choose a best option to declare a constant and after sometime this constant can create a issue for you in code due to its scope or any other reason. On the other hand you may have a fixed mind that you always declare a constant in a same way in any situation like a love ma...

Background: Now days compilation process for any language is divided into two parts and same is applicable for objective c. Frontend Compiler (Clang) Backend Compiler (LLVM) Frontend Compiler (Clang):  Responsibility of front-end compiler is to take a source code and convert into intermediate representation (IR).  In case of clang it is LLVM IR.  Backend Compiler(LLVM):  Responsibility of backend compiler is to take a IR as input and convert into object code. LLVM input is bitstream of LLVM IR (Bitcode) and output is sequence of machine instruction(Object code). Each  cpu or processor has different set of  M achine   instruction, So  LLVM output is CPU dependent or it can be executed on specific CPU only.   There may be question in your mind that  1) What is the need to divide into these phases? 2) What is LLVM IR? Can we see the LLVM IR as Output? What is the need to divid...

Animation Animation always capture the user attention. We can use animation to update things on the screen.  For developer also animations fascinated things to learn and implement. Today we will try shake effect with Various  API. CABasicAnimation: Here we animate view's frame y coordinate from one position to another position. It is simple example of changing the position with respect to time. CABasic Animation is deal with the single keyframe.                                        y(t) = y 0 + t*d(y) You can use CABasic Animation if you have to play with single value. You need to move object from  one position to another without any intermediate steps. CABasicAnimation * shakeAnimation = [CABasicAnimation animationWithKeyPath: @ "position" ]; shakeAnimation . duration = 0.05 ; shakeAnimation . autoreverses = YES; shakeAnimation . repe...

Blocks Blocks are executable code just like a function.  It can be written inside a function or we can store the reference in a variable and call it later.  But wait a minute these all functionality we can achieve by function pointer and functions.  Then what is so special about blocks? Let first go through how we can define blocks. int (^sum)( int , int ) = ^( int number1, int number2){ return number1+number2; }; The above block can be used to find the sum of two numbers.  If we recall the function pointer in c then it is very much similar to above: int sumFunction ( int number1, int number2){ return number1+number2; } int (*sum) ( int , int ) = sumFunction; //Function Pointer *sum Then Why we need Blocks if we already have Function pointer?  1) B locks can capture variables from the enclosing scope by simply referring to them within the block. How ? Let see the next Section 2)  Blocks...

GCD: A library to provide support for concurrent code execution on multicore hardware in iOS. It provides an easier mechanism to access multi-thread environment without taking the overhead of lock and unlock shared data, create a thread and perform a task like that. If we use  NSThread or pthread in the application then we need to take care of so much point. Like if I need to execute 10 tasks concurrently in my application. How much thread pool I require, how to synchronise two tasks while using threads. It provides methods to add a task in a queue. 1) Dispatch Async 2) Dispatch Sync  Dispatch Async: This method is used to add a block for asynchronous execution and return immediately. If you used this method to add a block then it will return immediately and does not wait for execution of the block. If you do not want to wait for the execution of the block then you can use this method to add operation in a dispatch queue. - ( void ) performMyTask{ ...