单例中的委托模式不起作用

Question

20140115 updated: with working code

I have a Singleton where I want to use the delegate pattern. When I call the methode with the delegate I get not notified.

Where is my error? How can I get the delegate pattern to work with didComposition ?

Below my debugger and code, the important parts:

Debugger

2014-01-15 14:31:09.703 Foobar[5854:70b] -[WebApi sandbox] [Line 42] Sandbox call
2014-01-15 14:31:09.707 Foobar[5854:70b] -[WebApi getSurroundStream] [Line 67] Surround Stream call

WebApi.h - Singleton with the delegate pattern

#import "AFHTTPRequestOperationManager.h"

@class WebApi;
@protocol WebApiDelegate <NSObject>

-(void)didComposition;

@end

@interface WebApi : AFHTTPRequestOperationManager <SingletonDelegate>

@property (assign, nonatomic)id<WebApiDelegate> delegate;

+(WebApi*)sharedInstance;

-(void)sandbox;
-(void)doSurroundComposition;

@end

WebApi.m

#import "WebApi.h"
#define kApiHost @"http://192.168.0.1"  

@implementation WebApi

-(WebApi*)initWithBaseURL:url {
    self = [super init];
    if (self != nil) { }
    return  self;
}

#pragma mark - Singleton methods
+(WebApi*)sharedInstance
{
    static WebApi *sharedInstance = nil;
    static dispatch_once_t oncePredicate;
    dispatch_once(&oncePredicate, ^{
        sharedInstance = [[self alloc] initWithBaseURL:[NSURL URLWithString:kApiHost]];
    });

    return sharedInstance;
}

-(void)sandbox {

    DLog(@"Sandbox called"); 
    // Do AFNetworking Stuff
}

-(void)doSurroundComposition {
    [self sandbox]; 
    DLog(@"do surround composition");
    [self.delegate performSelector:@selector(didComposition)];
}

@end

SurroundViewController.h

    #import <UIKit/UIKit.h>
    #import "Lokation.h"
    #import "WebApi.h"

    @interface SurroundViewController : UICollectionViewController <LokationDelegate, WebApiDelegate>

    @property (strong, nonatomic) Lokation *lokation;

    @end

SurroundViewController.m (updated with working code)

#import "SurroundViewController.h"
#import "SWRevealViewController.h"

@interface SurroundViewController ()

@end

@implementation SurroundViewController

-(id)init
{
    self = [super init];
    if (self) {
        // Custom initialization
        self.lokation = [[Lokation alloc] init];
        self.lokation.delegate = self;
        [self.lokation getLocation];
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    [WebApi sharedInstance].delegate = self;
    [[WebApi sharedInstance] doSurroundComposition];

}

-(void)didComposition {
    DLog(@"did load composition");  // will not be called!
}

@end

Answer 1

When you call [WebApi sharedInstance] for the first time, you then need to set the delegate to something. Currently (in the code you show) you aren't setting any delegate. So when the shared instance tries to call the delegate it is simply a no-op.