Qt的信号和槽参数类型，确实常引用预选赛事项？ [英] Argument type for Qt signal and slot, does const reference qualifiers matters?

问题描述

有关信号及以下类型的插槽

For signal and slot of below type

signals:
    void textChanged(const QString &);

public slots:
    void setText(const QString & text)

框TextChanged和的setText的参数的类型似乎工作的的常量的和的＆放invarable; 的。是否常和参考资格作出任何差别相比，只是使用QString的？

the type of argument of textChanged and setText seems to work invarable of const and &. Does the constant and reference qualification make any difference compared to just using QString ?

QObject::connect(a,SIGNAL(textChanged(QString)),b,SLOT(setText(QString)));
QObject::connect(a,SIGNAL(textChanged(const QString &)),b,SLOT(setText(const QString &)));

编辑：
我没有注意到输出窗口显示错误信息时，有信号或SLOT正在使用不兼容的类型。我以为信号插槽机制能够在编译时检测参数类型的错误。

I did not notice the output window showing error messages when there is incompatible type being used in SIGNAL or SLOT. I thought the signal slot mechanism is capable of detecting argument type error at compile time.

推荐答案

Qt的检查一个标准化签名 ，这意味着

Qt checks a normalized signature, meaning

正常化减少空白到
  最小，移动'常量'前线
  在适当情况下，删除'常量'
  从值类型和常量替换
  其值引用。

Normalization reduces whitespace to a minimum, moves 'const' to the front where appropriate, removes 'const' from value types and replaces const references with values.

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