QAbstractSpinBox 的函数验证

Question

我正在阅读 QT Docu

中的这个函数

它说

QValidator::State QAbstractSpinBox::validate(QString &input, int &pos) const [virtual]

This virtual function is called by the QAbstractSpinBox to determine whether input is valid. The pos parameter indicates the position in the string. Reimplemented in the various subclasses.

我有一个奇怪的问题，因为我不太理解文档。这里的input是一个字符串，我们判断input是否有效。那么，为什么我们需要字符串中的位置呢？我以为这里的pos是字符串的长度，但是调试的时候发现不是。那么这里的pos是什么意思呢？

更新：

感谢@mohabouje。在我的例子中，我使用了从 QAbstractSpinBox 继承的 class，我重写了这个方法并希望在更改后验证字符串。我如何更新此 pos 以进行验证？

QValidator::State MySpinBox::validate( QString &input, int &pos ) const
{
    QString pureValue = stripped( input, &tmpPos, prefix(), suffix() );  //this is my function, i just want to remove also prefix and suffix 
    //I want to add group separator into the pureValue and validate it after that
    //I want to add group separator here, not in the constructor with setGroupSeparatorShown(true);
    //When i add group separator here, the separator appears simultaneously when we type
    //When i set setGroupSeparatorShown(true) in the constructor, it appears after we finish editing and move to another thing (this element loses focus) 
    pureValue.insert(3, locale().groupSeparator());
    input = pureValue;
    
     // I think now 'pos' has changed, how could I update 'pos' to call the following function?
     QValidator::State state = QDoubleSpinBox::validate( input, pos );
     return state;
}

Answer 1

我对底层实现很好奇。我查看了 github 中的源代码。

QVariant QDoubleSpinBoxPrivate::validateAndInterpret(QString &input, int &pos,
                                                     QValidator::State &state) const
{
    if (cachedText == input && !input.isEmpty()) {
        state = cachedState;
        QSBDEBUG() << "cachedText was '" << cachedText << "' state was "
                   << state << " and value was " << cachedValue;
        return cachedValue;
    }
    const double max = maximum.toDouble();
    const double min = minimum.toDouble();

    QString copy = stripped(input, &pos);
    QSBDEBUG() << "input" << input << "copy" << copy;
    int len = copy.size();
    ...
}

这些参数在名为 stripped 的私有函数中使用。这是源代码：

QString QAbstractSpinBoxPrivate::stripped(const QString &t, int *pos) const
{
    QString text = t;
    if (specialValueText.size() == 0 || text != specialValueText) {
        int from = 0;
        int size = text.size();
        bool changed = false;
        if (prefix.size() && text.startsWith(prefix)) {
            from += prefix.size();
            size -= from;
            changed = true;
        }
        if (suffix.size() && text.endsWith(suffix)) {
            size -= suffix.size();
            changed = true;
        }
        if (changed)
            text = text.mid(from, size);
    }

    const int s = text.size();
    text = text.trimmed();
    if (pos)
        (*pos) -= (s - text.size());
    return text;

}

因此，如果我理解正确，给定一个字符串和 prefix/suffix 配置，该函数将获取该字符串并计算要验证的数据的实际大小，忽略前缀和后缀。

函数returns已经验证的数据可以被解析以计算数值。

pos的原始值，函数减去待校验文本大小与裁剪后文本大小的差值

QAbstractSpinBox 的函数验证

Function validate of QAbstractSpinBox

qt

qdoublespinbox