从无形或非形式单位的函数返回值

Question

嗨我不知道如何调用函数在无形或非形式单位返回值。

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; 
} 

我无法找到此问题的解决方案或教程。 你有更好的吗？ Clement

Answer 1

当前文件组织很好。

你应该改变行：

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

到：

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

第一种形式给出了错误：

E2885: Invalid pointer addition

自"\nYour yard is "类型是char *和你在指针上添加一个数字（看看Borland C++ Builder 6 and string concatenation更多详情请参阅Concatenate two string literals）。

如果使用String，则operator+将被重载，并且将指向char的指针添加到String已被很好地定义。

EDIT

USHORT类型在windows.h定义。您应该添加：

#include <windows.h> 

在 Unit3.h

，或者更好，使用标准的C++类型（unsigned FindArea(unsigned l, unsigned w)）。