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What's the basic difference between the two..? it would be nice if can someone explain using the example of NSInteger and NSNumber.. Thanks

Community
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Ankit Srivastava
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5 Answers5

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The main difference is related to where they stay in the memory, objects are stored in the heap while value type are stored directly in the Stack ...

heap : is an area of memory used for dynamic memory allocation.

stack : is the section of memory that is allocated for automatic variables within functions. Data is stored in stack using the Last In First Out (LIFO) method.

About NSInteger and NSNumber :

NSInteger is nothing more than a synonym for a long integer, while NSNumber is an Objective-C class, a subclass of NSValue to be specific.

aleroot
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    Not main difference and in some cases not true at all.. NSInteger *i = malloc(sizeof(NSInteger)); NSString *constString = @"constString"; - quite opposite to what you said. – Oleg Trakhman Jun 14 '12 at 11:09
  • Of course you can force a value type to stay on the heap, but it is not the default behavior ... In your example you are manually allocating memory and declaring a pointer to an NSInteger , you are not using the value type, but the pointer to access a memory address ... – aleroot Jun 14 '12 at 11:13
  • 1) Memory type is still not the main difference of objects and Plain old data types. 2) In many languages for example C++ objects can be allocated in stack. And it's default behavior there. 3) In some cases Objective-C objects can be allocated in stack. – Oleg Trakhman Jun 14 '12 at 11:32
  • This is not a particularly useful distinction to draw. A primitive-typed ivar will be on the heap, with the object that holds it. – jscs Jun 14 '12 at 19:23
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object is : member data + function operating on the data

so, primitive data type is just data, no method directly related to it.

object is something like a module, include the data and function (method here).

NSInteger is primitive data type. NSNumber is object, it's member data maybe NSInteger.

Wubao Li
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Primitive data types store a direct value, for example NSInteger stores an integer value (either a 32 bit Integer, or a 64 bit Integer depending on the compiled architecture), Objects are an instance of a class, with methods, properties, etc.

In order to get an NSInteger from an NSNumber, you would use

[aNumber intValue];
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Primitive data types are used for storing fundamental types of data, such as strings, integers, and real numbers. So when you declare a value type variable, the compiler sets aside, or allocates, a chunk of memory that is big enough for that variable. The way reference types work is different. When you are working with a reference type, you are using two things, an object that is created in memory and a variable that references to the object. The variable does not hold an actual piece of data with which your program will work. Instead it holds a special value known as a reference, which links the variable to the object.

Annia Martinez
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Primitive data type is just a data while object type is know as reference type.
Which is a class which have two behavior data member and member function.

Abhishek
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