1.字典的创建

     /*
     字典：保存数据的一种工具
     分类：不可变字典、可变字典
     详情：通过键(key)-值(value)的形式存储数据
    
     
     注意：
     1、value可以相同，key必须唯一
     2、字典保存对象类型
     3、key一般为字符串
     4、字典中的多个key-value是没有顺序的
     */

不可变字典

   //创建空字典
    NSDictionary *dic1 = [NSDictionary dictionary];
    NSDictionary *dic2 = [[NSDictionary alloc] init];
    
    
    //对像方法创建
    NSDictionary *dic3 = [[NSDictionary alloc] initWithObjectsAndKeys:@"sunck", @"1", @"is", @"2", @"a", @"3", @"good", @"4", @"man", @"5", nil];
    NSLog(@"dic3 = %@", dic3);
    
    
    //注意：前后两个数组（数据，键值）一一对应的
    NSDictionary *dic4 = [[NSDictionary alloc] initWithObjects:@[@"sunck", @"is", @"a", @"good", @"man"] forKeys:@[@"1", @"2", @"3", @"4", @"5"]];
    
    //通过已存在的字典创建新的字典
    NSDictionary *dic5 = [[NSDictionary alloc] initWithDictionary:dic4];
    
    
    //类方法：
    NSDictionary *dic6 = [NSDictionary dictionaryWithObjectsAndKeys:@"sunck", @"1", @"is", @"2", @"a", @"3", @"good", @"4", @"man", @"5", nil];
    NSDictionary *dic7 = [NSDictionary dictionaryWithObjects:@[@"sunck", @"is", @"a", @"good", @"man"] forKeys:@[@"1", @"2", @"3", @"4", @"5"]];
    NSDictionary *dic8 = [NSDictionary dictionaryWithDictionary:dic4];
    
    //注意：键值之间用:链接，多个键值对用,分隔，最后省略了nil
    NSDictionary *dic9 = @{@"1": @"sunck", @"2": @"is", @"3": @"a", @"4": @"good", @"5": @"man"};

不可变字典的其他方法

  //取值
  NSDictionary *dic1 = @{@"1": @"sunck", @"2": @"is", @"3": @"a", @"4": @"good", @"5": @"man", @"6": @"Oh", @"7": @"he", @"8": @"is", @"9": @"good"};
  NSLog(@"dic1 = %@", dic1);
  //取一个值
  NSString *str = [dic1 objectForKey:@"3"];
  NSString *str2 = dic1[4];
  
  //取多个值
  NSArray * arr1 = [dic1 objectsForKeys:@[@"1",@"2",@"3"] notFoundMarker:@"NotFound"];
  //取s所有的值
  NSArray *value = [dic1 allValues];
  //取所有的key
  NSArray *key = [dic1 allKeys];
  //取出所有value对应的key
  NSArray *key3 = [dic1 allKeysForObject:@"sdd"];
  
  //遍历字典
  //针对字典来说，in的前面是字典中的key
  //in的后面是要遍历的集合(数组、字典)
  for (NSString *key in dic1) {
    NSString *value = [dic1 objectForKey:key];
  }
  
  //枚举遍历
  NSEnumerator *emumer = [dic1 keyEnumerator];
  id keyString = nil;
  while (keyString = [emumer nextObject]) {
    NSString *value = [dic1 objectForKey:keyString ];
  }

2.可变字典的增删改查

//增
  NSMutableDictionary *mutDic = [[NSMutableDictionary alloc]initWithObjects:@[@"sun", @"is", @"a", @"good", @"man"] forKeys:@[@"1", @"2", @"3", @"4", @"5"]];
  //增加一个键值对
  [mutDic setObject:@"sdf" forKey:@"7"];
  //增加多个键值对,
  //注意：如果增加时，键值对键一样，原数据会被修改为当前数据
  [mutDic addEntriesFromDictionary:@{@"6":@"sdf",@"3":@"sdf"}];
  
  //删
  [mutDic removeObjectForKey:@"6"];
  //删除多个
  [mutDic removeObjectsForKeys:@"6",@"5"];
  //删除所有的
  [mutDic removeAllObjects];
  //改
  NSMutableDictionary *mutDic3 = [[NSMutableDictionary alloc] initWithObjects:@[@"sunck", @"is", @"a", @"good", @"man", @"!"] forKeys:@[@"1", @"2", @"3", @"4", @"5", @"6"]];
  [mutDic3 setObject:@"nice" forKey:@"4"];
  NSLog(@"mutDic3-1 = %@", mutDic3);
  [mutDic3 setValue:@"handsome" forKey:@"4"];
  NSLog(@"mutDic3-2 = %@", mutDic3);
  
  //将字典替换为后面的字典
  [mutDic3 setDictionary:mutDic1];