NSApplication subclass with additional delegate methods for various useful things.

GSTApplication.h

//
//  GSTApplication.h
//  Ingist
//
//  Created by Brent Royal-Gordon on 7/12/13.
//  Copyright (c) 2013 Architechies. All rights reserved.
//

#import <Cocoa/Cocoa.h>
#import "GSTServicesProvider.h"

@protocol GSTApplicationDelegate;

@interface GSTApplication : NSApplication

@property (strong) id <GSTApplicationDelegate> delegate;

@end


@protocol GSTApplicationDelegate <NSApplicationDelegate>

@optional
- (void)gst_application:(GSTApplication *)app openURL:(NSURL*)URL;
- (GSTServiceHandler)gst_application:(GSTApplication *)app handlerForServiceNamed:(NSString*)name;
- (void)gst_applicationShowHelp:(GSTApplication *)app;

@end

GSTApplication.m

//
//  GSTApplication.m
//  Ingist
//
//  Created by Brent Royal-Gordon on 7/12/13.
//  Copyright (c) 2013 Architechies. All rights reserved.
//

#import "GSTApplication.h"

@interface GSTApplication () <GSTServicesProviderDelegate>

@end

@implementation GSTApplication

@dynamic delegate;

- (void)didReceiveGetURLEvent:(NSAppleEventDescriptor*)URLEvent replyEvent:(NSAppleEventDescriptor*)replyEvent {
    NSString * URLString = [[URLEvent paramDescriptorForKeyword:keyDirectObject] stringValue];
    NSURL * URL = [NSURL URLWithString:URLString];
    if([self.delegate respondsToSelector:@selector(gst_application:openURL:)]) {
        [self.delegate gst_application:self openURL:URL];
    }
}

- (void)finishLaunching {
    [NSAppleEventManager.sharedAppleEventManager setEventHandler:self andSelector:@selector(didReceiveGetURLEvent:replyEvent:) forEventClass:kInternetEventClass andEventID:kAEGetURL];
    
    GSTServicesProvider.sharedServicesProvider.delegate = self;
    self.servicesProvider = GSTServicesProvider.sharedServicesProvider;
    
    [super finishLaunching];
}

- (GSTServiceHandler)servicesProvider:(GSTServicesProvider *)serviceProvider handlerForServiceNamed:(NSString *)name {
    if(![self.delegate respondsToSelector:@selector(gst_application:handlerForServiceNamed:)]) {
        return nil;
    }
    
    return [self.delegate gst_application:self handlerForServiceNamed:name];
}

- (void)showHelp:(id)sender {
    if([self.delegate respondsToSelector:@selector(gst_applicationShowHelp:)]) {
        [self.delegate gst_applicationShowHelp:self];
        return;
    }
    
    [super showHelp:sender];
}

@end

GSTServicesProvider.h

//
//  GSTServiceProvider.h
//  Ingist
//
//  Created by Brent Royal-Gordon on 7/25/13.
//  Copyright (c) 2013 Architechies. All rights reserved.
//

#import <Foundation/Foundation.h>

typedef void (^GSTServiceHandler)(NSPasteboard * pboard, NSString * userData, NSError ** error);

@protocol GSTServicesProviderDelegate;

@interface GSTServicesProvider : NSObject

@property (weak) id <GSTServicesProviderDelegate> delegate;
+ (instancetype)sharedServicesProvider;

@end

@protocol GSTServicesProviderDelegate <NSObject>

- (GSTServiceHandler)servicesProvider:(GSTServicesProvider*)serviceProvider handlerForServiceNamed:(NSString*)name;

@end

GSTServicesProvider.m

//
//  GSTServiceProvider.m
//  Ingist
//
//  Created by Brent Royal-Gordon on 7/25/13.
//  Copyright (c) 2013 Architechies. All rights reserved.
//

#import "GSTServicesProvider.h"
#import <objc/runtime.h>

@interface GSTServicesProvider ()

@property (strong, nonatomic) NSMutableDictionary * serviceHandlers;

@end

@implementation GSTServicesProvider

+ (NSString *)serviceNameForSelector:(SEL)aSelector {
    NSString * selectorName = NSStringFromSelector(aSelector);
    NSRange range = [selectorName rangeOfString:@":userData:error:" options:NSAnchoredSearch|NSBackwardsSearch];
    
    if(range.location == NSNotFound) {
        return nil;
    }
    
    return [selectorName substringToIndex:range.location];
}

- (GSTServiceHandler)handlerForServiceNamed:(NSString*)name {
    GSTServiceHandler handler = self.serviceHandlers[name];
    
    if(!handler) {
        handler = [[self.delegate servicesProvider:self handlerForServiceNamed:name] copy];
        self.serviceHandlers[name] = handler;
    }
    
    return handler;
}

+ (BOOL)resolveInstanceMethod:(SEL)sel {
    NSString * serviceName = [self.class serviceNameForSelector:sel];
    
    if(!serviceName) {
        return [super resolveInstanceMethod:sel];
    }
    
    IMP imp = imp_implementationWithBlock(^(GSTServicesProvider * self, NSPasteboard * pboard, NSString * userData, NSError ** error) {
        GSTServiceHandler handler = [self handlerForServiceNamed:serviceName];
        if(!handler) {
            [self doesNotRecognizeSelector:sel];
            return;
        }
        
        handler(pboard, userData, error);
    });
    
    NSString * str = [NSString stringWithFormat:@"%s%s%s%s%s%s", @encode(void), @encode(id), @encode(SEL), @encode(id), @encode(id), @encode(__autoreleasing id *)];
    class_addMethod(self, sel, imp, str.UTF8String);
    
    return YES;
}

- (BOOL)respondsToSelector:(SEL)aSelector {
    NSString * serviceName = [self.class serviceNameForSelector:aSelector];
    
    if(serviceName && ![self handlerForServiceNamed:serviceName]) {
        return NO;
    }
    
    return [super respondsToSelector:aSelector];
}

- (id)initSingleton {
    if((self = [super init])) {
        _serviceHandlers = [NSMutableDictionary new];
    }
    return self;
}

+ (id)allocWithZone:(NSZone *)zone {
    static GSTServicesProvider * singleton;
    static dispatch_once_t once;
    
    dispatch_once(&once, ^{
        singleton = [[super allocWithZone:zone] initSingleton];
    });
    
    return singleton;
}

- (id)init {
    return self;
}

+ (instancetype)sharedServicesProvider {
    return [self new];
}

@end

@brentdax
Hi!
Could you explain is this example about .servicesProvider property of NSApplication?
I still can't figure out how to implement "servicesProvider" method. See

As I understand, ServicesProvider uses dynamic dispatching by filtering methods with 3 parameters ( pasteboard, userData and error ).
Is it correct?

Thanks!

P.S. It would be nice if you replied with simple ServicesProvider which do nothing but print to console its parameters.