为什么在使用 QString::right 的字符串开头省略逗号? [英] Why a comma is omitted at the beginning of a string using QString::right?

问题描述

回答 QString 替换引号之外的字符 我偶然发现了一个奇怪的行为.

Answering QString replace characters outside of quotes I have stumbled upon a strange behavior.

执行此代码:

foreach (const QString &key, json.keys()) {
    const QJsonValue &value(json.value(key));

    qDebug() << key << value.toString().right(key.length());
}

使用这个 json，A:

QJsonObject json {
    {"thing1", "thing1value1"},
    {"thing2", "thing2value2"},
    {"thing3", "thing3value3"}
};

和这个json，B(注意thing2后面的逗号):

and with this json, B (notice the comma after thing2):

QJsonObject json {
    {"thing1", "thing1value1"},
    {"thing2", "thing2,value2"},
    {"thing3", "thing3value3"}
};

在这两种情况下都会产生:

in both cases produces:

"thing1" "value1"
"thing2" "value2"
"thing3" "value3"

不应该:

"thing1" "value1"
"thing2" ",value2"
"thing3" "value3"

在第二种情况下，B?

推荐答案

QString::right 函数

返回包含字符串的 n 最右边 个字符的子字符串.

Returns a substring that contains the n rightmost characters of the string.

_{[特别强调我的]}

由于key字符串的长度是6，那么6最右边的字符将被返回，给你"value2"，没有逗号.

Since the length of the key string is 6, then the 6 rightmost characters will be returned, giving you "value2" without the comma.

如果你想得到没有前导键的字符串，你可以使用 mid 代替:

If you want to get the string without the leading key you could use mid instead:

value.toString().mid(key.length())

对于您的用例，我宁愿建议 midRef，因为实际上不需要创建子字符串的副本.

For your use-case I would rather suggest midRef, since there's no need to actually create a copy of the sub-string.

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