objective c设计模式--KVC

KVC
什么是KVC
设置key value
- (void) setValue:(id) value forKey:(NSString *) key;   //类似于set方法
- (id) valueForKey: (NSString *) key;      //类似于get方法
- (void) setValue: (id) value forKeyPath: (NSString *) keyPath;
设置undefined key
- (void) setValue: (id) value forUndefinedKey:(NSString *)key;//当key不存在时
设置一组keys
-(void) setValuesForKeysWithDictionary:(NSDictionary *) keyedValues;
-(NSDictionary *) dictionaryWithValuesForKeys: (NSArray *) keys;
根据情况是否触发KVO
+ (BOOL) automaticallyNotifiesObserversForKey:(NSString *)key ；

//缺省是返回yes

下面有一个例子：

例子描述的是关于节目表和节目列表之间的关系：

PlayItem.h

@interface PlayItem :NSObject

{

    NSString *_name;

    float _price;

}

@property (nonatomic,retain)NSString *name;

@property (nonatomic,assign)float price;

@end

PlayItem.m

#import <Foundation/Foundation.h>

#import "PlayItem.h"

@implementation PlayItem

@synthesize name = _name;

@synthesize price = _price;

- (void)dealloc{

    self.name = nil;

    [super dealloc];

}

//如果设置里面不存在的key就会调用该方法

- (void) setValue:(id)value forUndefinedKey:(NSString *)key

{

    NSLog(@"function %@ is calling.",NSStringFromSelector(_cmd));

}

@end

PlayList.h

#import <Foundation/Foundation.h>

#import "PlayItem.h"

@interface PlayList : NSObject

{

    int _number;

    NSString *_name;

    PlayItem *_currentItem;//当前播放列表

    NSMutableArray *_itemList;

}

@property (nonatomic,retain) NSMutableArray *itemList;

@property (nonatomic,assign) int number;

@property (nonatomic,retain) NSString *name;

@property (nonatomic,retain) PlayItem *currentItem;

@end

PlayList.m

#import "PlayList.h"

@implementation PlayList

@synthesize itemList = _itemList,number = _number,name = _name,currentItem = _currentItem;

-(void) dealloc {

    self.currentItem = nil;

    self.itemList = nil;

    self.name = nil;

    [super dealloc];

}

- (id)init{

    self = [super init];

    if (self) {

        self.currentItem = [[[PlayItem alloc]init]autorelease];

        self.itemList = [NSMutableArray array];

        for (int i = 0; i <20; i++) {

            PlayItem *pi = [[PlayItem alloc] init];

            pi.name = [NSString stringWithFormat:@"name %i",i];

            pi.price = 100+i;

            [self.itemList addObject:pi];

            [pi release];

        }

    }

    return self;

}

//调用setValue:forKey:方法时，参数key不存在时调用此方法

-(void)setValue:(id)value forUndefinedKey:(NSString *)key

{

    NSLog(@"file %s function %@ is calling.",__FILE__,NSStringFromSelector(_cmd));

}

@end

main.m

#import "PlayList.h"

#import "PlayItem.h"

int main ()

{

    @autoreleasepool {

 PlayList *pl = [[PlayList alloc] init];

        [pl setValue:@"大连实德" forKey:@"_name"];//forKey可以改为forKeyPath

        

        NSLog(@"pl name:%@",pl.name);

        id v = [pl valueForKey:@"number"];

        NSLog(@"number: %@",v);

        

        

        //设置pl.currentItem.name字段

        [pl setValue:@"当前播放列表" forKeyPath:@"currentItem.name"];

        //forKeyPath不可以改为forKey

        NSLog(@"pi.currentItem.name:%@",pl.currentItem.name);

        

        

        //设置一批key值

        NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:@"dalianshide",@"name",@"90",@"number", nil];

        [pl setValuesForKeysWithDictionary:dict];

        NSLog(@"number is :%i,name is :%@",pl.number,pl.name);

        

        

        //如果对象中没有key

        [pl setValue:@"aishide " forKey:@"test"];

        id obj= [pl valueForKey:@"itemList"];

        NSLog(@"itemList:%@,%@",pl.itemList,obj);

        

        id obj2 = [pl.itemList valueForKeyPath:@"_name"];

        //id obj2 = [pl valueForKeyPath:@"itemList.name"];

        NSLog(@"itemList.name:%@",obj2);

        NSLog(@"itemList price sum is %@",[pl.itemList valueForKeyPath:@"@sum.price"]);

        //@sum.price来对pl.itemList中所有price的进行求和

        NSLog(@"itemList price avg is %@",[pl.itemList valueForKeyPath:@"@avg.price"]);

        NSLog(@"itemList price max is %@",[pl.itemList valueForKeyPath:@"@max.price"]);

        NSLog(@"itemList price min is %@",[pl.itemList valueForKeyPath:@"@min.price"]);

    }

    

    return 0;

}