Objective-C performSelector Guide

performSelector is a method in the NSObject class that is used to call a specific method on the current thread.

Principle:
The principle of the `performSelector` method is to leverage Objective-C’s messaging mechanism. When calling the `performSelector` method, runtime will dynamically search for and call the corresponding method based on the method’s name and parameter types. Therefore, we can use the `performSelector` method to dynamically call methods without the need to hardcode the method calls during coding.

Usage:
The performSelector method has multiple overloads, which can be selected based on actual needs. Several commonly used usages are as follows:

1. performSelector method with no arguments:

- (void)performSelector:(SEL)aSelector

This method can be used to call a method with no parameters. For example:

[self performSelector:@selector(doSomething)];

Equivalent to:

[self doSomething];

1. performSelector method with one parameter:

- (void)performSelector:(SEL)aSelector withObject:(id)anObject

This usage can be applied to invoke a method with one parameter. For example:

[self performSelector:@selector(doSomethingWithObject:) withObject:obj];

Equivalent to:

[self doSomethingWithObject:obj];

1. Using the performSelector method with multiple arguments:

- (void)performSelector:(SEL)aSelector withObject:(id)anObject1 withObject:(id)anObject2

This method can be used to call methods with multiple parameters. For example:

[self performSelector:@selector(doSomethingWithObject1:object2:) withObject:obj1 withObject:obj2];

Equivalent to:

[self doSomethingWithObject1:obj1 object2:obj2];

It is important to note that when using the performSelector method, it performs selector checking and parameter type matching. If the selector cannot be found or the parameter types do not match, it will lead to a program crash. To avoid this situation, you can use the respondsToSelector method to determine if an object has implemented a specific method.