传值

传值、传址

procedure Tform1.myproc1(i: string); //传值
begin
  i:= 'A' ; 
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  x: string;
begin
  x:= edit1.Text;
  myproc1(x);   //x只过来报信，把2送来，无变化
  edit2.Text:= x;  //结果为：2
end;

procedure Tform1.myproc2(var i: string); //传址
begin
  i:= 'A' ;  //变量替换
end;

procedure TForm1.Button2Click(Sender: TObject);
var
  x: string;
begin
  x:= edit1.Text;
  myproc2(x);  //x过来报信且住了一宿，变化了
  edit3.Text:= x;  //结果为：A
end;

procedure tform1.myproc3(const i: string); //const
begin
  i:= 'A' ;   //const为常量，常量不能赋值常量
end;

function tform1.GetNum1(i: integer):integer; //传值
begin
  i:=i+10;
  result:=i;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  x,y:integer;
begin
  x:=20;
  y:=GetNum1(x);  //x只过来报信，把2送来，无变化

  edit1.Text:= inttostr(x);
  edit2.Text:= inttostr(y);
end;

function tform1.GetNum2(var i: integer):integer; //传址
begin
  i:=i+10;
  result:=i;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  x,y:integer;
begin
  x:=20;
  y:=GetNum2(x);  //x过来报信且住了一宿，变化了

  edit1.Text:= inttostr(x);
  edit2.Text:= inttostr(y);
end;

默认参数

function getsum(x:integer=20;y:integer=30;z:integer=40):integer;
begin
  result:=x+y+z;
end;

procedure TForm1.Button1Click(Sender:TObject);
var
  iSum:integer;
begin
  iSum:=getsum;∥结果为90，这时x、y、z均取的默认值
  iSum:=getsum(10):/结果为80，这时y、z取的默认值
  iSum:=getsum(10,20);∥结果为70，这时z取的默认值
  iSum:=getsum(10,20,30);/结果为60
end;