NSMutableDictionary是可变词典。
NSMutableDictionary是NSDictionary的子类。

说明:
表中的key、key1、key2、obj、obj1和obj2是任意对象，size是一个NSUInteger无符号整数。

示例

#import <Foundation/Foundation.h>

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        // 创建一个空的可变词典, 注意：key不能为nil
        NSMutableDictionary *glossary = [NSMutableDictionary dictionary];
        
        // 存储3个条目在类别中
        /*
        [glossary setObject: @"A class defined so other classes can inherit from it"
                     forKey: @"abstract class"];
        
        [glossary setObject: @"To implement all the methods defined in a protocol"
                     forKey: @"adopt"];
        
        [glossary setObject: @"Storing an object for later use"
                     forKey: @"archiving"];
         */
        // 与上面的语法等价
        glossary[@"abstract class"] = @"A class defined so other classes can inherit from it";
        glossary[@"adopt"] = @"To implement all the methods defined in a protocol";
        glossary[@"archiving"] = @"Storing an object for later use";
        
        // 检索并显示它们
        /*
        NSLog(@"abstract class: %@", [glossary objectForKey: @"abstract class"]);
        NSLog(@"adopt: %@", [glossary objectForKey: @"adopt"]);
        NSLog(@"archiving: %@", [glossary objectForKey: @"archiving"]);
         */
        // 与上面的语法等价
        NSLog(@"abstract class: %@", glossary[@"abstract class"]);
        NSLog(@"adopt: %@", glossary[@"adopt"]);
        NSLog(@"archiving: %@", glossary[@"archiving"]);
    }
    return 0;
}

运行测试