private property in Objective C

I implement my private properties like this.

MyClass.m

@interface MyClass ()

@property (nonatomic, retain) NSArray *someArray;

@end

@implementation MyClass

@synthesize someArray;

...

That's all you need.

A. If you want a completely private variable. Don't give it a property.
B. If you want a readonly variable that is accessible external from the encapsulation of the class, use a combination of the global variable and the property:

//Header    
@interface Class{     
     NSObject *_aProperty     
}

@property (nonatomic, readonly) NSObject *aProperty;

// In the implementation    
@synthesize aProperty = _aProperty; //Naming convention prefix _ supported 2012 by Apple.

Using the readonly modifier we can now access the property anywhere externally.

Class *c = [[Class alloc]init];    
NSObject *obj = c.aProperty;     //Readonly

But internally we cannot set aProperty inside the Class:

// In the implementation    
self.aProperty = [[NSObject alloc]init]; //Gives Compiler warning. Cannot write to property because of readonly modifier.

//Solution:
_aProperty = [[NSObject alloc]init]; //Bypass property and access the global variable directly

private property in Objective C

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