问题
Can anyone please clarify me that where exactly the variables stored in objective c ?
In .h file
@interface example: NSObject
{
NString *string; // where is this stored
int number; // where is this stored
}
@property (nonatomic,strong) NSURL* mURL; // where is this stored
@end
similarly,
In .m file
# import "xyz.h"
NSString *constant = @"hello"; // where is this stored
@interface example()
{
NString *textg; // where is this stored
int numb; // where is this stored
}
@property (nonatomic,strong) NSURL* sURL; // where is this stored
@end
回答1:
"string", "textg", "number" and "numb" are instance variables to the class. The difference is that "string" and "number" are eligible to be publicly accessible (via ref->number), and "textg" and "numb" are private (since other classes conventionally do not #import .m files).
"mURL" and "sURL" properties are stored as instance variables "_mURL" and "_sURL". Again, "_mURL" is eligible to be publicly accessible (via ref->_mURL), and "_sURL" is not for the same reason.
And, "constant" is an ordinary global variable stored on the heap.
回答2:
You ask:
where exactly the variables stored
To answer just this: all the variables other than constant, and the variables used by the properties, are stored as part of the memory allocation for each instance of your class example that you create. Every instance has its own copy of each variable. E.g. when you do:
example *anExample = [example new];
You are requesting that an instance of example is created and a reference to it is stored in anExample. That instance contains the all the instance variables and properties you have declared (and it also contains any instance variables and properties for its superclasses, in this just just NSObject).
Your other variable, constant, is declared at the file level. Such variables are stored along with the compiled code in your file as part of your application. Regardless of how many instances of your class are created there is only ever one constant variable. Methods running on behalf of any instance all see the same constant variable.
HTH
来源：https://stackoverflow.com/questions/27773335/storage-of-objective-c-property-variables-and-non-property-variables