黑马程序员_NSDictionary

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创建

创建四个轮胎对象放进NSDictionary

Tire *t1 = [Tire new];Tire *t2 = [Tire new];Tire *t3 = [Tire new];Tire *t4 = [Tire new];NSDictionary *tires = [NSDictionary dictionaryWithObject:t1,@“front-left”,t2@“front-right”,t3,@“back-left”,t4,@“back-right”,nil];//也可以使用NSDictionary *tires = @{@“front-left”,t1,@“front-right”,t2,@“back-left”,t3,@“back-right”,t4};

查找

- (id) objectForKey: (id) aKey;

或者tires[key];for

假如查找右后方轮胎可以这样:

Tire *tire = [tires objvetForKey:@"back-ringt"];

或者是

Tire *tire = tires[@"back-right"];

假如字典里没有右后方轮胎，则返回nil值。

可变性

与NSMutableString和NSMutableArray一样，NSDictionary对应也有一个NSMutableDictionary

创建

+ (id) DictionaryWithCapacity: (NSUInteger) numItems;

NSMutableDictionary *tires = [DictionaryWithCapacity:10];

还有一种

NSMutableDictionary *tires = [NSMutableDictionary dictionary];

添加

- (void)setObject:(id)anObject forKey:(id)

NSMutableDictionary *tires = [NSMutableDictionary dictionary];[tires setObject:t1 forKey:@"front-left"];<pre name="code" class="objc">[tires setObject:t2 forKey:@"front-right"];

[tires setObject:t3 forKey:@"back-left"];

[tires setObject:t4 forKey:@"back-right"];

对已有的关键字使用setObject:forKey:方法，那么方法就会用新的值替换掉原有得数值。

删除

-(void) removeObjectForKey: (id) aKey;

删除左后方的轮胎

[tires removeObjectForKey:@"back-left"];

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