QT，C++不能在沒有對象的情況下調用成員函數

Question

在我的mainwindow.cpp中是調用的地方。呼叫應該發生在點擊按鈕的事件上。錯誤說cannot call member function 'void Foo::setFooAttributes(A&, B&, C&, D&)' without object。

void MainWindow::on_generateButton_clicked() 
{ 

    setCreator(ui->interfaceCreatorName->text()); 
    setAlternateName(ui->interfaceAlternateName->text()); 
    setDomain(ui->interfaceDomain->text().toInt()); 
    QString filename = getCreator() + "'s " + getAlternateName() + ".txt"; 
    QFile file(filename); 
    A a; B b; C c; D d; 
    Foo::setFooAttributes(a,b,c,d); //ERROR: cannot call member function without object 
    generateTop(file); 
    generateMiddle(file); 
    generateSecondaryMid(file); 
    generateLast(file); 
    generateTertiaryMid(file, a, b, c, d); 

} 

函數本身看起來像這樣：

void Foo::setFooAttributes(A &aFoo, B &bFoo, C &cFoo, D &dFoo){ 

    aFoo.stopPoint = MainWindow.ui->aInterfaceStopPoint->text().toDouble(); 
    aFoo.rate = MainWindow.ui->aInterfaceRate->text().toInt(); 
    aFoo.domain = MainWindow.ui->aInterfaceDomain->text().toInt(); 
    aFoo.length = MainWindow.ui->aInterfaceLength->text().toInt(); 

    bFoo.stopPoint = MainWindow.ui->bInterfaceStopPoint->text().toDouble(); 
    bFoo.rate = MainWindow.ui->bInterfaceRate->text().toInt(); 
    bFoo.domain = MainWindow.ui->bInterfaceDomain->text().toInt(); 
    bFoo.length = MainWindow.ui->bInterfaceLength->text().toInt(); 

    cFoo.stopPoint = MainWindow.ui->cInterfaceStopPoint->text().toDouble(); 
    cFoo.rate = MainWindow.ui->cInterfaceRate->text().toInt(); 
    cFoo.domain = MainWindow.ui->cInterfaceDomain->text().toInt(); 
    cFoo.length = MainWindow.ui->cInterfaceLength->text().toInt(); 

    dFoo.stopPoint = MainWindow.ui->dInterfaceStopPoint->text().toDouble(); 
    dFoo.rate = MainWindow.ui->dInterfaceRate->text().toInt(); 
    dFoo.domain = MainWindow.ui->dInterfaceDomain->text().toInt(); 
    dFoo.length = MainWindow.ui->dInterfaceLength->text().toInt(); 

} 

我把代碼的其餘部分，包括貼在這裏pastebin source

我第一次嘗試調用setFooAttributes(a,b,c,d);沒有Foo::但是這給了我foo.h中錯誤如'setFooAttributes' was not declared in this scope

Answer 1

讓你的Foo::setFooAttributes a static mem ber函數，因爲它不在「this」實例上運行。

當你在這，你可能會考慮刪除所有重複，以更好地遵循DRY（不要重複自己）原則：

template <typename A> static void Foo::setFooAttributes(A &aFoo, int iface) { 

    aFoo.stopPoint = MainWindow.ui->interfaceStopPoint[iface]->text().toDouble(); 
    aFoo.rate = MainWindow.ui->interfaceRate[iface]->text().toInt(); 
    aFoo.domain = MainWindow.ui->interfaceDomain[iface]->text().toInt(); 
    aFoo.length = MainWindow.ui->interfaceLength[iface]->text().toInt(); 

} 

static void Foo::setFooAttributes(A &aFoo, B &bFoo, C &cFoo, D &dFoo){ 

    setFooAttributes(aFoo, 0); 
    setFooAttributes(bFoo, 1); 
    setFooAttributes(cFoo, 2); 
    setFooAttributes(dFoo, 3); 
} 

（這需要你到每個{a,b,c,d}InterfaceStopPoint轉換，{a,b,c,d}InterfaceRate,{a,b,c,d}InterfaceDomain和{a,b,c,d}InterfaceLength）轉換爲數組，而不是四個單獨的變量）。

你甚至可以通過使用循環或變量模板函數來改善這一點，但我會把它作爲練習。