NGAAutoObserver.m #1

//
//  NGAAutoObserver.m
//  P4Menu
//
//  Created by Michael Bishop on 10/3/11.
//  Copyright 2011 __MyCompanyName__. All rights reserved.
//

#import "NGAAutoObserver.h"
#import "NGAUtilities.h"
#import <objc/runtime.h>

NSString * const kObserverMethodPrefix = @"valueDidChangeFor";

static NSString * keyPathFromSelectorName(NSString * selectorName)
{
    NSScanner * scanner = [NSScanner scannerWithString:selectorName];
    if (! [scanner scanString:kObserverMethodPrefix intoString:nil] )
        return nil;
    
    NSString * keyPath = [[[selectorName substringFromIndex:[scanner scanLocation]] NGA_stringByConvertingFirstWordToLowerCase] stringByReplacingOccurrencesOfString:@"_" withString:@"."];
    
    if ( [keyPath hasSuffix:@":"] )
        keyPath = [keyPath substringToIndex:[keyPath length] - 1];
        
        return keyPath;
}

static NSString * selectorNameFromKeyPath(NSString * keyPath)
{
    NSString * selectorName = [kObserverMethodPrefix stringByAppendingString:[[keyPath NGA_stringByConvertingFirstCharacterToUpperCase] stringByReplacingOccurrencesOfString:@"." withString:@"_"] ];
    
    return selectorName;
}

@interface NGAAutoObserver : NSObject {
}
+(NGAAutoObserver*)sharedAutoObserver;

-(void)registerObserverMethodsForObject:(id)object;
-(void)deregisterObserverMethodsForObject:(id)object;

@end

@implementation NGAAutoObserver

SINGLETON_IMPLEMENTATION(NGAAutoObserver, sharedAutoObserver)

- (id)init
{
    self = [super init];
    if (self) {
    }
    
    return self;
}

DEALLOC (
)

//-(void)enumeratePropertiesOfClass:(Class)class usingBlock:(void(^)(NSString * propertyName))block
//{
//    unsigned int propertyCount = 0;
//    objc_property_t * propertyList = class_copyPropertyList(class, &propertyCount);
//    objc_property_t * currentProperty = propertyList;
//    while (propertyCount > 0)
//    {
//        const char * propertyNameCString = property_getName(*currentProperty);
//        NSString * propertyName = [NSString stringWithUTF8String:propertyNameCString];
//        block( propertyName );
//        currentProperty++;
//        propertyCount--;
//    }
//    
//    free( propertyList );
//}

-(void)registerObserverMethodsOnObject:(id)object forKeyPaths:(NSArray*)keyPaths
{
    for (NSString * keyPath in keyPaths)
    {
        [object addObserver:self forKeyPath:keyPath options:NSKeyValueObservingOptionNew|NSKeyValueObservingOptionOld context:NULL];
    }
}

-(void)deregisterObserverMethodsOnObject:(id)object forKeyPaths:(NSArray*)keyPaths
{
    for (NSString * keyPath in keyPaths)
    {
        [object removeObserver:self forKeyPath:keyPath];
    }
}

-(void)enumerateMethodsOfClass:(Class)class usingBlock:(void(^)(SEL selector))block
{
    unsigned int methodCount = 0;
    Method * methodList = class_copyMethodList(class, &methodCount);
    Method * currentMethod = methodList;
    while (methodCount > 0)
    {
        SEL selector = method_getName(*currentMethod);
        block( selector );
        currentMethod++;
        methodCount--;
    }
    
    free( methodList );
}

-(void)registerObserverMethodsForObject:(id)object
{
    [self enumerateMethodsOfClass:[object class] usingBlock:^(SEL selector) {

        NSString * keyPath = keyPathFromSelectorName(NSStringFromSelector(selector));

        if ( !keyPath )
            return;

        [object addObserver:self forKeyPath:keyPath options:NSKeyValueObservingOptionNew|NSKeyValueObservingOptionOld context:NULL];
    }];
}

-(void)deregisterObserverMethodsForObject:(id)object
{
    [self enumerateMethodsOfClass:[object class] usingBlock:^(SEL selector) {

        NSString * keyPath = keyPathFromSelectorName(NSStringFromSelector(selector));

        if ( !keyPath )
            return;

        [object removeObserver:self forKeyPath:keyPath];
    }];
}

-(void)observeValueForKeyPath:(NSString *)keyPath
                     ofObject:(id)object
                       change:(NSDictionary *)change
                      context:(void *)context
{
    NSString * selectorName = selectorNameFromKeyPath(keyPath);
    
    if ([object respondsToSelector:NSSelectorFromString(selectorName)])
        [[NSInvocation invocationWithSelectorName:selectorName target:object] invoke];

    selectorName = [selectorName stringByAppendingString:@":"];

    if ([object respondsToSelector:NSSelectorFromString(selectorName)])
    {
        NSInvocation * invocation = [NSInvocation invocationWithSelectorName:selectorName target:object];
        [invocation setArgument:&change atIndex:2];
        [invocation invoke];
    }
}

@end


@implementation NSObject (NGAAutoObservation)

-(void)registerObserverMethodsForKeyPaths:(NSArray*)keyPaths
{
    [[NGAAutoObserver sharedAutoObserver] registerObserverMethodsOnObject:self forKeyPaths:keyPaths];
}

-(void)deregisterObserverMethodsForKeyPaths:(NSArray*)keyPaths
{
    [[NGAAutoObserver sharedAutoObserver] deregisterObserverMethodsOnObject:self forKeyPaths:keyPaths];
}

-(void)registerAllAutoObservationMethods
{
    [[NGAAutoObserver sharedAutoObserver] registerObserverMethodsForObject:self];
}

-(void)unregisterAllAutoObservationMethods
{
    [[NGAAutoObserver sharedAutoObserver] deregisterObserverMethodsForObject:self];
}

@end