IOS about decorating the agent with weak or assign

For this question, the code that I saw yesterday by my friend was occasionally noticed. I usually use weak to decorate, but he used the assign for a moment do not know right and wrong. and then I searched for a bit. Here's a list of results.

For weak: Indicates that the object is not responsible for keeping delegate this object, delegate the destruction of this object is externally controlled.

For strong: The object strongly references delegate, the delegate object cannot be destroyed by the outside world, resulting in a circular reference (Retain Cycles)

For assing: There is also the weak effect. But there is assign on the net is the pointer assignment, does not have the reference count operation, after the use if does not set to nil, may produce the wild pointer, but once the weak does not use, will never use, will not produce the wild pointer. The above is their own search to see the answer, who has a better argument, can evaluate the reply. Adopt quality advice.

IOS about decorating the agent with weak or assign