從無形或非形式單位的函數返回值

Question

嗨我不知道如何調用函數在無形或非形式單位返回值。

Unit1.h

#ifndef Unit1H 
#define Unit1H 
//--------------------------------------------------------------------------- 
#include <System.Classes.hpp> 
#include <Vcl.Controls.hpp> 
#include <Vcl.StdCtrls.hpp> 
#include <Vcl.Forms.hpp> 
//--------------------------------------------------------------------------- 
class TForm1 : public TForm 
{ 
__published: // IDE-managed Components 
    TButton *Button2; 
    TLabel *Label2; 
    void __fastcall Button2Click(TObject *Sender); 
private: // User declarations 
public:  // User declarations 
    __fastcall TForm1(TComponent* Owner); 
}; 
//--------------------------------------------------------------------------- 
extern PACKAGE TForm1 *Form1; 
//--------------------------------------------------------------------------- 
#endif 

Unit1.cpp

//--------------------------------------------------------------------------- 

#include <vcl.h> 
#pragma hdrstop 

#include "Unit1.h" 
#include "Unit3.h" 

//--------------------------------------------------------------------------- 
#pragma package(smart_init) 
#pragma resource "*.dfm" 
TForm1 *Form1; 
//--------------------------------------------------------------------------- 
__fastcall TForm1::TForm1(TComponent* Owner) 
: TForm(Owner) 
{ 

} 

//--------------------------------------------------------------------------- 
void __fastcall TForm1::Button2Click(TObject *Sender) 
{ 
    USHORT lengthOfYard; 
    USHORT widthOfYard; 
    USHORT areaOfYard; 

    widthOfYard = 15; 
    lengthOfYard = 17; 
    areaOfYard= FindArea(lengthOfYard,widthOfYard); 
    Label2->Caption = "\nYour yard is "+ areaOfYard +" square feet\n\n"; 

} 
//--------------------------------------------------------------------------- 

Unit3.h

//--------------------------------------------------------------------------- 
#ifndef Unit3H 
#define Unit3H 
//--------------------------------------------------------------------------- 

// declare the function here in the header file. 

USHORT FindArea(USHORT length, USHORT width); //function prototype 

#endif//--------------------------------------------------------------------------- 

Unit3.cpp

//--------------------------------------------------------------------------- 

#pragma hdrstop 

#include "Unit3.h" 
//--------------------------------------------------------------------------- 
#pragma package(smart_init) 

USHORT FindArea(USHORT l, USHORT w) 
{ 
    return l * w; 
} 

我無法找到此問題的解決方案或教程。 你有更好的嗎？ Clement

Answer 1

當前文件組織很好。

你應該改變行：

Label2->Caption = "\nYour yard is " + areaOfYard + " square feet\n\n"; 

到：

Label2->Caption = "\nYour yard is " + String(areaOfYard) + " square feet\n\n"; 

第一種形式給出了錯誤：

E2885: Invalid pointer addition

自"\nYour yard is "類型是char *和你在指針上添加一個數字（看看Borland C++ Builder 6 and string concatenation更多詳情請參閱Concatenate two string literals）。

如果使用String，則operator+將被重載，並且將指向char的指針添加到String已被很好地定義。

EDIT

USHORT類型在windows.h定義。您應該添加：

#include <windows.h> 

在 Unit3.h

，或者更好，使用標準的C++類型（unsigned FindArea(unsigned l, unsigned w)）。