使用 NSDictionary 的下标

Created: November-22, 2018

下标也可以与 NSDictionary 和 NSMutableDictionary 一起使用。以下代码：

NSMutableDictionary *myDictionary = [@{@"Foo": @"Bar"} mutableCopy];
[myDictionary setObject:@"Baz" forKey:@"Foo"];
NSLog(@"%@", [myDictionary objectForKey:@"Foo"]); // Baz

可以缩短为：

NSMutableDictionary *myDictionary = [@{@"Foo": @"Bar"} mutableCopy];
myDictionary[@"Foo"] = @"Baz";
NSLog(@"%@", myDictionary[@"Foo"]); // Baz