问题
Whenever Apple creates its own custom classes, it often creates a pointer to the object instead of the actual object itself.
For example, instead of doing:
Class object
They often do:
Class *object = [[Class alloc] init];
Why are pointers so commonly used instead of putting the object on the stack? Is there some technical reason for this, because I don't see any immediate benefit of doing so.
EDIT: If Objective-C doesn't support objects on the stack how can they create any non-pointers? I mean I have seen people use NSInteger directly.
回答1:
Objective-C doesn't support objects on the stack.
Fantastic explanation on Mike Ash's blog here
回答2:
Objective-C regular usage make objects travel all over the place, they can be accessed, modified and managed from a million different places. Stack objects, by definition have only one owner and their life and availability is restricted to the function (thread) that spawned them. This would be a major problem in Obj-C since either the object lifespan would not be controlled, or the object lifespan would be the same as the application (have you seen how much memory those objects take?).
回答3:
The * (pointer) points to a spot in memory that this object is going to be saved to. Also, This is just the way that objective-c is written. Plus i believe that objective c doesnt allow you to put the object on the stack!
回答4:
if the object is passed around a lot it may be easier to use a pointer than passing a reference. When you know you are passing a pointer it indicates that things might get modified where as a pass by reference may be overlooked and cause things to change when you didn't want them to.
来源：https://stackoverflow.com/questions/9123079/using-pointers-in-objective-c