IOS Firebase : Loop all key in snapshot. 值位置困惑

Question

我从 Firebase 服务器收到快照，如下面的日志所示。现在我想循环快照中的所有键，但我的位置很乱。

我不知道为什么会这样。任何帮助将不胜感激

打印日志的代码

NSLog(@"snapshot = %@",snapshot.value);
for (NSString *keyPath in snapshot.value) {
     NSLog(@"keyPath = %@",keyPath);
}

这是日志

2016-04-20 11:48:04.177 EarCrush[5241:79090] snapshot = {
    "-KFlrXzqsSa50GVnJkqk" =     {
        conversationID = "2886-2377";
        text = Okteh;
        time = "20-04-2016 11:12";
    };
    "-KFlrgrvdR_uj2o1ltaw" =     {
        conversationID = "2886-2377";
        text = "How are you determining";
        time = "20-04-2016 11:12";
    };
    "-KFlrhSBbVnx4XyWjQPy" =     {
        conversationID = "2886-2377";
        text = "Message 2 ..... ";
        time = "20-04-2016 11:12";
    };
    "-KFlrhzx0TK5CeSR3aAA" =     {
        conversationID = "2886-2377";
        text = "Message 3: Hello world ";
        time = "20-04-2016 11:12";
    };
}
2016-04-20 11:48:04.177 EarCrush[5241:79090] keyPath = -KFlrhzx0TK5CeSR3aAA
2016-04-20 11:48:04.178 EarCrush[5241:79090] keyPath = -KFlrhSBbVnx4XyWjQPy
2016-04-20 11:48:04.179 EarCrush[5241:79090] keyPath = -KFlrXzqsSa50GVnJkqk
2016-04-20 11:48:04.179 EarCrush[5241:79090] keyPath = -KFlrgrvdR_uj2o1ltaw

Firebase 服务器图片

Answer 1

当您打印 FDataSnapshot 时，它会打印 JSON 结构。由于 JSON 没有为子节点定义顺序，因此它们的显示顺序是不确定的(尽管它经常会在您到达这里时按照它们键的字典顺序打印子节点)。

Firebase's queries可用于按特定顺序获取数据。例如来自 this question :

[[languagesRef queryOrderedByChild:@"distance"] observeEventType:FEventTypeValue withBlock:^(FDataSnapshot *snapshot) {

    for ( FDataSnapshot *child in snapshot.children) {

        NSLog(@"child.key = %@",child.key);

    }

Firebase 快照包含有关子数据排序的附加信息，打印该快照时不会显示这些信息。当您遍历快照的子项时，此排序信息用于确保上面循环中的正确顺序。