Keywords in IOS

In the development of iOS, every key word of the system is everywhere, but not every key word is so clear, so Luo listed some key words for everyone to learn from each other, there is imperfect place please correct me, thank you

Atomic	Atomic is a thread-protection technique used by OBJC, basically to prevent the data from being read by another thread when the write is not completed. This mechanism is resource-intensive, so nonatomic is a very good choice on small devices such as the iphone, if there is no communication programming between multiple threads.
Super	Calling a method of the parent class
ReadOnly	The Description property is read-only and the default tag is to read and write
ReadWrite	The Description property is read-write, which is also the default property
Retain	Frees the old object, assigns the value of the old object to the input object, and then increases the index count of the input object to 1
Self	is a hidden parameter that points to the class of the currently calling method
Setter	Sets the specified set method
Getter	Sets the specified Get method
Property	Set the properties of member variables (with read/write, assignment assign,retain,copy, and support for multithreading nonatomic)
End	The end of a class header file or implementation file
Copy	Create an object with an index count of 1 and then release the old object
Assign	Simple assignment without changing the reference count
Synthesize	According to the @property setting, the corresponding access method of the member variable is generated automatically, so that the member variable can be accessed conveniently using the point operator.
Import	Tell the preprocessor to include the contents of the header file in this file
Dynamic	Tell the compiler to implement the Access method by ourselves
Nonatomic	Non-atomic access, no lock on attribute assignment, multi-threaded concurrent access improves performance
Implementation	Indicates the implementation of the class
Strong	Strong references, as long as the last strong pointer no longer points to the object, then the object will be freed, and all weak pointers will be cleared
Weak	Weak references
__strong	is the default keyword
__weak	Declares a weak reference that can be automatically Nil.
__unsafe_unretained	Declares a weak application, but does not automatically nil, that is, if the area of memory pointed to is released, the pointer is a wild pointer.
__autoreleasing	Used to modify the parameters of a function, which is automatically released when the function returns.
unsafe_unretained	Weak references, easy to generate wild pointers, try to use less unsafe_unretained keywords
Synchronized	Method plus Lock

Keywords in IOS