Some trivia in objective-c (update)

2. Object (the instance object of the Class). In short, it's a piece of data in memory that holds the value of an attribute through an instance variable .

4. The use of the object. Create object------Send Message---------Release object (sets the variable that points to the object to nil)

   Note: The use of objects is not the direct manipulation of the object itself, but the manipulation of pointers to Objects!!! ( For example, the object contained in the array is not the object itself, but a pointer to the object)

6. Nil is a pointer to the value W of 0, and nil is a pointer indicating that no object is pointing. (corresponds to NULL in Null,java in C language)

8. Instance variables && Access instance variables && Point syntax && class methods and instance methods && specifying the method of an accident

10. Instancetype and ID: The former means that the method return type and the calling method object type are the same, used in the Init method

    The latter represents " pointers to arbitrary objects ". (void*)

12. Self: does not need to declare, exists in the method, is an implicit local variable, used to send the message to the object itself

14. "@[]" syntax: can only be used to create non-variable groups!
    

Some trivia in objective-c (update)