1.无修饰符----传指针,指针被复制一份入栈。函数内修改属性值后,仅仅是修改堆中数据的值,并没有复制堆中的数据,这点与string不同,留意。
2.const 修饰符---传指针,指针被复制一份入栈。与无修饰符一致,据说加上const编译器会优化。可加可不加!!
3.var修饰符-----直接把变量现在的内存编号传过去,就是说没有任何新指针或其它【入栈】。
4.out修饰符----------与var一样,传递过来的是现在变量本身。
unit Unit4; interface uses Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics, Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls; type TForm4 = class(TForm) Button1: TButton; Memo1: TMemo; procedure Button1Click(Sender: TObject); procedure FormCreate(Sender: TObject); private { Private declarations } public { Public declarations } end; /// <summary> /// 定义一个类 /// </summary> TPerson = class private Fname: string; Fage: Integer; Fsex: Boolean; procedure Setage(const Value: Integer); procedure Setname(const Value: string); procedure Setsex(const Value: Boolean); public property name: string read Fname write Setname; property age: Integer read Fage write Setage; property sex: Boolean read Fsex write Setsex; end; var Form4: TForm4; implementation {$R *.dfm} procedure abc1(ap: TPerson); begin ap.name := '李大嘴1'; end; procedure abc2(const ap: TPerson); begin ap.name := '李大嘴2'; end; procedure abc3(var ap: TPerson); begin ap.name := '李大嘴3'; end; procedure abc4(out ap: TPerson); var a: string; begin a := ap.name; ap.name := '李大嘴4'; end; procedure TForm4.Button1Click(Sender: TObject); var ps: TPerson; begin ps := TPerson.Create; ps.name := '小李飞刀'; ps.age := 29; ps.sex := True; abc4(ps); Memo1.Lines.Add(ps.name); //一定要再这里释放 ps.Free; end; { TPerson } procedure TPerson.Setage(const Value: Integer); begin Fage := Value; end; procedure TPerson.Setname(const Value: string); begin Fname := Value; end; procedure TPerson.Setsex(const Value: Boolean); begin Fsex := Value; end; procedure TForm4.FormCreate(Sender: TObject); begin ReportMemoryLeaksOnShutdown := True; end; end.
本文来自博客园,作者:del88,转载请注明原文链接:https://www.cnblogs.com/del88/p/6667724.html