Delphi XE2 - 繼承類不調用基類的構造函數...？

Question

創建一個繼承自另一個類的類時，是否應該在派生類創建時調用基類的構造函數？

Type 
    TBase = Class 
    constructor xMain; 
    End; 
    TDerived = Class(TBase) 
    constructor xMain; 
    End; 

constructor TBase.xMain; 
begin 
    MessageBox(0,'TBase','TBase',0); 
end; 

constructor TDerived.xMain; 
begin 
    MessageBox(0,'TDerived','TDerived',0); 
end; 


Var 
    xTClass:TDerived; 
begin 
    xTClass := TDerived.xMain; 
end. 

我認爲這應該導致MessageBox顯示「TBase」，然後「TDerived」。然而，事實並非如此。當上面的代碼運行時，它只會導致一個MessageBox顯示「TDerived」。

Answer 1

constructor TDerived.xMain; 
begin 
    inherited; 
    MessageBox(0,'TDerived','TDerived',0); 
end; 

Answer 2

add在TDerived.xMain中繼承;否則來自祖先的代碼將不會被調用;

begin 
    inherited;//call the ancestor TBase.xMain 
    MessageBox(0,'TDerived','TDerived',0); 
end; 

而且這個問題將有助於你理解繼承保留字：

Delphi: How to call inherited inherited ancestor on a virtual method?

另一個很好的資源是http://www.delphibasics.co.uk/RTL.asp?Name=Inherited