objective-c的NSDictionary， 为什么这段输出是null
NSDictionary*dict=[NSDictionarydictionaryWithObjectsAndKeys:@"jack",@"jackisaboy",@"j...
NSDictionary * dict = [NSDictionary dictionaryWithObjectsAndKeys:
@"jack", @"jack is a boy",
@"john", @"john is a boy",
@"lisa", @"lisa is a girl",
nil];
NSString * str = [dict objectForKey:@"john"];
NSLog(@"%@", str); 展开
@"jack", @"jack is a boy",
@"john", @"john is a boy",
@"lisa", @"lisa is a girl",
nil];
NSString * str = [dict objectForKey:@"john"];
NSLog(@"%@", str); 展开
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你太粗心了，ObjectsAndKeys:，前边是值，后边的是key，找不到你的:@"john"的
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NSDictionary * dict = [NSDictionary dictionaryWithObjectsAndKeys:
@"jack is a boy", @"jack",
@"john is a boy", @"john",
@"lisa is a girl", @"lisal",
nil];
NSString * str = [dict valueForKey:@"john"];
NSLog(@"%@", str);
//这样就能行，因为左边是value，右边是key
objectForKey 是通过key 找object
@"jack is a boy", @"jack",
@"john is a boy", @"john",
@"lisa is a girl", @"lisal",
nil];
NSString * str = [dict valueForKey:@"john"];
NSLog(@"%@", str);
//这样就能行，因为左边是value，右边是key
objectForKey 是通过key 找object
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