第三彈 NSDictionary字典類型 發射

NSDictionary字典類型可以將數據以鍵值對的形式儲存起來，取值的時候通過key就可以直接拿到對應的值，非常方便,在同一個詞典對象中可以保存多個不同類型的數據.

創建NSDictionary 與 取元素

// key 與 value  一一對應
    NSDictionary *dict1 = [NSDictionary dictionary];
    NSDictionary *dict2 = [NSDictionary dictionaryWithObject:@"zs" forKey:@"name"];
    NSDictionary *dict3 = [NSDictionary dictionaryWithObjects:@[@"zs",@"22",@"183"] forKeys:@[@"name",@"age",@"height"]];
    NSDictionary *dict4 = @{@"zs" : @"name", @"22" : @"age", @"183" : @"height"};
    NSLog(@"name=%@ age=%@ height=%@", dict3[@"name"], dict3[@"age"], dict3[@"height"]);
    NSLog(@"name=%@ age=%@ height=%@", [dict3 objectForKey:@"name"], [dict3 objectForKey:@"age"], [dict3 objectForKey:@"height"]);

遍歷字典元素

NSUInteger count = [dict3 count]; //取字典數量
//for循環取元素
for (int i = 0; i < count; ++i) {
    // 獲取字典中所有的key
    NSArray *keys = [dict3 allKeys];
    // 取出當前位置對應的key
    NSString *key = keys[i];
    NSString *value = dict3[key];
    NSLog(@"key = %@, value = %@", key, value);
}
// 如何通過forin遍歷字典
for (NSString *key in dict3) {
    NSString *value = dict3[key];
    NSLog(@"key = %@, value = %@", key, value);
}  
/**
 *  使用OC字典的迭代器來遍歷  官方推薦使用
 *
 *  @param key  鍵
 *  @param obj  value 值
 *  @param stop 控制停止
 */
[dict3 enumerateKeysAndObjectsUsingBlock:^(id  _Nonnull key, id  _Nonnull obj, BOOL * _Nonnull stop) {
    NSLog(@"key = %@, value = %@", key, obj);
}];

字典和文件

//將字典寫入文件
[dict3 writeToFile:@"/Users/xxx/Desktop/dict.plist" atomically:YES];
//從文件中讀取字典
NSDictionary *dictFile = [NSDictionary dictionaryWithContentsOfFile:@"/Users/xxx/Desktop/dict.plist"];

可變字典 NSMutableDictionary

//創建可變字典
NSMutableDictionary *mDict = [NSMutableDictionary dictionary];
[mDict setObject:@"zs" forKey:@"name"]; //同名的key賦值, 那么新值會覆蓋舊值
[mDict setValuesForKeysWithDictionary:@{@"age":@"22",@"height":@"183"}];
NSMutableDictionary *mdict = [NSMutableDictionary dictionaryWithObjects:@[@"zs", @"ls"] forKeys:@[@"name", @"name"]];
NSLog(@"mdit = %@",mdict); //ls
//取數據
[mDict valueForKey:@"name"];
NSLog(@"age = %@", mDict[@"age"]);
//刪除數據
[mDict removeObjectForKey:@"name"];
[mDict removeAllObjects];
//不可變字典出現了同名的key, 那么后面的key對應的值不會被保存
NSDictionary *dictM = @{@"name":@"zs", @"name":@"ls"};
NSLog(@"dictM = %@", dictM); // name = zs

MarkDown文本和代碼均可在github上下載：GitHub地址 : CoderVan