Dark Horse Programmer----protocol-protocol

1. Definition of the Agreement

@protocol Agreement name <NSObject>
Method List ...
@end

2. How to comply with an agreement

1> Class Compliance Agreement
@interface Class Name: Parent class name < protocol name 1, protocol name 2>

@end

2> Protocol Compliance Agreement
@protocol protocol Name < Protocol 1, protocol name 2>

@end

3. Keywords for method declarations in the agreement

1> @required (default)
Requires the implementation method, if not implemented, there will be a warning

2> @optional
No implementation method required

4. When defining a variable, limit the object that this variable holds to a protocol

Class name < protocol name > * variable name;
ID < protocol name > variable name;

If the corresponding protocol is not followed, the compiler warns

5. Attributes declared in the @property can also be used as a limitation of compliance with the agreement

@property (Nonatomic, Strong) class name < protocol name > * attribute name;
@property (nonatomic, strong) id< protocol name > attribute name;

6. The agreement can be defined in a separate. h file, or in a class
1> If this protocol is used only in a class, the protocol should be defined in that class

2> If this protocol is used in many classes, it should be defined in a separate. h file

7. Classifications can be defined in separate. h and. m files and can also be defined in the original class
1> generally, it is defined in a separate file, because the function of classification is to extend the method without changing the original class.

2> defined in the original classification, only requires to be able to understand the grammar

Dark Horse Programmer----protocol-protocol