NGAValuePropagator.m #1

//
//  NGAValuePropagator.m
//
//  Created by Michael Bishop on 11/3/11.
//  Copyright (c) 2011 Numerical Garden LLC. All rights reserved.
//

#import "NGAValuePropagator.h"
#import "NGAUtilities.h"

@interface NGAValuePropagator : NSObject {
    NSMutableDictionary * bindings;
}
+(NGAValuePropagator*)sharedBinder;
-(BOOL)addPropagationOfValueForKeyPath:(NSString*)keyPath ofObject:(id)object toKeyPath:(NSString*)secondKeyPath ofObject:(id)secondObject;
@end

@implementation NGAValuePropagator

SINGLETON_IMPLEMENTATION(NGAValuePropagator, sharedBinder);

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

    bindings = [NSMutableDictionary new];
    
    return self;
}

-(void)dealloc
{
    [bindings dealloc];
    [super dealloc];
}

-(BOOL)addPropagationOfValueForKeyPath:(NSString*)keyPath ofObject:(id)object toKeyPath:(NSString*)secondKeyPath ofObject:(id)secondObject
{
    NSArray * source = [NSArray arrayFromFirstObject:[NSValue valueWithNonretainedObject:object] secondObject:keyPath];
    NSArray * target = [NSArray arrayFromFirstObject:[NSValue valueWithNonretainedObject:secondObject] secondObject:secondKeyPath];
    
    NSSet * bindingTargets = [bindings objectForKey:source];
    
    if ( bindingTargets )
    {
        if ( [bindingTargets containsObject:target] )
            return NO;
        bindingTargets = [bindingTargets setByAddingObject:target];
    }
    else
    {
        bindingTargets = [NSSet setWithObject:target];
    }
    
    [bindings setObject:bindingTargets forKey:source];
    
    [object addObserver:self forKeyPath:keyPath options:NSKeyValueObservingOptionNew context:NULL];
    
    [secondObject setValue:[object valueForKeyPath:keyPath] forKeyPath:secondKeyPath];
    return YES;
}

-(BOOL)removePropagationOfValueForKeyPath:(NSString*)keyPath ofObject:(id)object toKeyPath:(NSString*)secondKeyPath ofObject:(id)secondObject
{
    NSArray * source = [NSArray arrayFromFirstObject:[NSValue valueWithNonretainedObject:object] secondObject:keyPath];
    
    NSArray * target = [NSArray arrayFromFirstObject:[NSValue valueWithNonretainedObject:secondObject] secondObject:secondKeyPath];

    NSSet * bindingTargets = [bindings objectForKey:source];

    if (!bindingTargets || ![bindingTargets containsObject:target])
        return NO;
    
    bindingTargets = [bindingTargets setByRemovingObject:target];

    [bindings setObject:bindingTargets forKey:source];
    
    [object removeObserver:self forKeyPath:keyPath];

    return YES;
}

-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
    NSArray * source = [NSArray arrayFromFirstObject:[NSValue valueWithNonretainedObject:object] secondObject:keyPath];

    NSSet * bindingTargets = [bindings objectForKey:source];
    
    if ( !bindingTargets )
    {
        [super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
        return;
    }
    
    id newValue = [change objectForKey:NSKeyValueChangeNewKey];
    if ( [newValue isEqual:[NSNull null]] )
          newValue = nil;
    
    for (NSArray * target in bindingTargets )
    {
        [[[target firstObject] nonretainedObjectValue] setValue:newValue forKeyPath:[target secondObject]];
    }
}

@end

@implementation NSObject (NGASimpleBinding)

-(BOOL)addPropagationOfValueForKeyPath:(NSString*)keyPath intoTargetObject:(id)target keyPath:(NSString*)targetKeyPath
{
    return [[NGAValuePropagator sharedBinder] addPropagationOfValueForKeyPath:keyPath ofObject:self toKeyPath:targetKeyPath ofObject:target];
}

-(BOOL)removePropagationOfValueForKeyPath:(NSString*)keyPath intoTargetObject:(id)target keyPath:(NSString*)targetKeyPath
{
    return [[NGAValuePropagator sharedBinder] removePropagationOfValueForKeyPath:keyPath ofObject:self toKeyPath:targetKeyPath ofObject:target];
}
@end