observe.m

gistfile1.m

#import <Foundation/Foundation.h>

@interface FKItem : NSObject

@property(nonatomic) NSString * name;
@property(nonatomic) int price;

@end

@implementation FKItem

@synthesize name;
@synthesize price;

@end


@interface FKObserve: NSObject

@property (nonatomic, weak) FKItem * item;

-(void) showItemInfo;

@end

@implementation FKObserve

@synthesize item = _item;

- (void) showItemInfo
{
    NSLog(@"物品名称: %@, 价格为: %d", [_item name], [_item price]);
}

- (void) setItem:(FKItem *)item
{
//    self.item = item;
    
    [self.item addObserver:self forKeyPath:@"name" options:NSKeyValueObservingOptionNew context:nil];
    [self.init addObserver:self forKeyPath:@"price" options:NSKeyValueObservingOptionNew context:nil];
}

- (void) observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
    NSLog(@"----observe 方法被调用");
    
    NSLog(@"被修改的keyPath为: %@", keyPath);
    NSLog(@"被修改的对象为:  %@", object);
    NSLog(@"被修改的属性值为: %@", change);
    NSLog(@"context: %@", context);
}

@end

int main (int argc, char * argv[])
{
    @autoreleasepool {
        FKItem * item = [[FKItem alloc] init];
        [item setName:@"你好"];
        [item setPrice:109];
        NSLog(@"%@", item.name);
        FKObserve * ob = [[FKObserve alloc] init];
        [ob setItem:item];
        [ob showItemInfo];
        [item setName:@"新你好"];
        [item setPrice:119];
        NSLog(@"东西呢?");
    }
}




clang -fobjc-arc -framework Foundation FKOberve.m