In this blog i will discuss the following
- What is a Property?
- Why is it used?
- How to declare a property in Objective C?
What is a Property?
Property is a value that is used for specific purpose although its use may differ from one program to another. With property you can assign a value and extract a value
Why to use a property?
Well if your having a java or C# background then you must have read books which say that property is used for information hiding, i think that their are better ways of information hiding rather than using a property (My own view).
While using a property in java or in C# you used to write its getter and setter methods, well in Objective C its totally different.
Let's have a look at an example to see how property works in objective C.
In this example i am trying to add two numbers and the data will be coming from the property, just refer the sample code with comments that i have used to explain property
@interface Myclass : NSObject
{
int num1, num2; //global variables of integer type
}
@property (readwrite,assign) int num1, num2; //set the property for those integer variable
//you use assign in a case where you cannot retain the value like BOOL or NSRect, else use retain
//If you use retain then you become the owner of that particular property and you must release that property once its use is over.
-(void)add; //add function
@end
Implementation part of the class
@implementation Myclass
@synthesize num1, num2; //synthesize will automatically set getter and setter for your property
-(void)add
{
int result= num1+num2;
NSLog(@"Result of addition is %d",result);
}
@end
The final touch that's our main method
int main (int argc, const char * argv[]) {
NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
Myclass *obj_Myclass = [[Myclass alloc]init];
[pool addObject:obj_Myclass]; //adding object to the pool
obj_Myclass.num1 = 10; //invoking setter method
obj_Myclass.num2 = 20; //invoking setter method
[obj_Myclass add]; //calling the add method
[pool drain];
return 0;
}
Their might also be a scenario where you want the property to be read only, well that again is very easy.
The below given code will make your property read only
@property (readonly,assign) int num1, num2;
You can change the value directly by referencing it directly, refer the code below
-(void)add
{
self->num1 = 10; //legal
self->num2 =20; //legal
int result= num1+num2;
NSLog(@"Result of addition is %d",result);
}
Well this was about the properties in Objective C, if i get to know any more details on properties i will surely update the blog regarding the same....
