Ios:runtime Run time

1. What is a runtime runtime?

Runtime is a relatively low level of pure C language API, belongs to 1 C language Library, contains a lot of the underlying C language API.
In the OC code that we usually write, in the process of running the program, in fact, it turns into the runtime's C language code, runtime is OC's behind-the-scenes workers

For example, in the following method of creating an object, the Alloc method and the Init method are ultimately implemented by sending a message at runtime (message mechanism)

1 // OC: 2 [[Ljperson alloc] init];   3//Runtime: Import <objc/runtime.h> 4 objc_msgsend with runtime (objc_ Msgsend ("Ljperson", "Alloc"), "Init");

What's the use of 2.runtime?
Runtime is the bottom of the OC and can perform some very low-level operations (with OC is not realistic, bad implementation)

• Dynamically create a class during the program's run (for example, the KVO implementation)

• Dynamically adding properties \ Methods to a class, modifying property values \ Method \ method implementation during program run

• Traverse all member variables (properties) of a class \ All methods
  * Code can refer to Mjextention framework

• Exchange two implementations of the methods (mainly used to make some modifications to the system's own methods)

Functions commonly used in 3.runtime:

• Objc_msgsend: Sending a message to an object
• Class_copymethodlist: Traversing all methods of a class
• Class_copyivarlist: Traversing all member variables of a class
• Class_getclassmethod: Obtaining class methods for a class
• Class_getinstancemethod: Obtaining an object method for a class
• Class_getmethodimplementation: Obtaining the implementation of a method of a class ;
• Method_setimplementation: Setting the implementation of a method
  
• Method_exchangeimplementations: Implementation of two methods of exchange

4. Application Examples:

Waiting to be written ...

Ios:runtime Run time