IOS-use of callback functions

The data callback or proxy mode in IOS is mostly implemented by a callback function or block (code block), there is nothing to say about the block, syntax, here is a simple understanding of how the callback function works.

(This callback function works in fact the process of proxy mode.)

First, the implementation of the proxy class

First, create a new proxy class and write a protocol in it: Agencyprotocol

@protocol Agencyprotocol <nsobject>-(void) cometruesuccess: (NSString *) str; -(void) Cometruefail: (NSString *) str; @end

Then operate in the proxy class:

1. Introduce the AGENCYPROTOCOL protocol and define a proxy for the Agencyprotocol Protocol (delegate);
2. Use singleton mode for the proxy class (the General proxy class uses the singleton mode better, can prevent the memory leak);
3. Implement an Agent method;

. h File Code:

@protocol Agencyprotocol; @interface  IDdelegate; // Singleton mode + (ID) shareinstance; /* * *   Analog Proxy method * *  @param str    Indicates the parameters passed in *  */-(void) Agencyfunction: ( NSString *) str andbool: (BOOL) Isbool; @end

. m file Code:(the proxy implementation here is the most important part of the callback function)

@implementationAgencyclass#pragmaMark-Singleton modeStaticAgencyclass *instnce;+ (ID) shareinstance {if(Instnce = =Nil) {instnce= [[[Selfclass] [alloc] init]; }    returninstnce;}#pragmaMark-Proxy implementation-(void) Agencyfunction: (NSString *) str andbool: (BOOL) Isbool {if(isbool) {//call the Respondstoselector method to determine if the cometruesuccess is implemented and implement it if it is not implemented        if([Self.Delegaterespondstoselector: @selector (cometruesuccess:)]) {[Self.DelegateCOMETRUESUCCESS:STR]; }    } Else {        //call the Respondstoselector method to determine if the Cometruefail is implemented and implement it if it is not implemented        if([Self.Delegaterespondstoselector: @selector (cometruefail:)]) {[Self.DelegateCOMETRUEFAIL:STR]; }    }}@end

Second, the implementation of the use of the class

First, we introduce the proxy class in the. h file, and introduce the Protocol

#import " AgencyClass.h " @interface viewcontroller:uiviewcontroller<agencyprotocol>@end

Then we can manipulate in. m files

1. Create an object for the proxy class;
2. The delegate that will be used to assign the class to the proxy class;
3. Using proxy methods

// using proxy classes         // creating an Object    for a proxy class Agencyclass *agency = [Agencyclass shareinstance];         // The delegate that will be used to assign the class to the proxy class;    Agency. delegate = self ;         // using proxy methods    [Agency agencyfunction:@ " really in the implementation?"  [ Andbool:yes];

The last two ways we can implement a protocol

#pragma mark-agencyprotocol implementation-(void) cometruesuccess: (NSString *) str {    NSLog (@ "  %@ Yes, the operation was successful!  ", str);} -(void) Cometruefail: (NSString *) str {    NSLog (@ "%@ Sorry, the operation failed "  , str);}

IOS-use of callback functions