在 case 语句中使用字符串
非常遗憾 Delphi 的 case 语句不支持字符串, 但我觉得这也可能是基于效率的考量;
如果非要在 case 中使用字符串, 也不是不可以变通, 这里提供了五种方法.
本例效果图:
![](https://images.cnblogs.com/cnblogs_com/del/142973/o_8781.gif)
代码文件:
窗体文件:
如果非要在 case 中使用字符串, 也不是不可以变通, 这里提供了五种方法.
本例效果图:
![](https://images.cnblogs.com/cnblogs_com/del/142973/o_8781.gif)
代码文件:
unit Unit1; interface uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls, ExtCtrls; type TForm1 = class(TForm) RadioGroup1: TRadioGroup; Button1: TButton; Button2: TButton; Button3: TButton; Button4: TButton; Button5: TButton; Button6: TButton; procedure FormCreate(Sender: TObject); procedure Button1Click(Sender: TObject); procedure Button2Click(Sender: TObject); procedure Button3Click(Sender: TObject); procedure Button4Click(Sender: TObject); procedure Button5Click(Sender: TObject); procedure Button6Click(Sender: TObject); end; var Form1: TForm1; implementation {$R *.dfm} uses TypInfo; {操作枚举用} {初始化一个单选组, 用于测试} procedure TForm1.FormCreate(Sender: TObject); begin RadioGroup1.Items.CommaText := 'a,bb,ccc,dddd'; RadioGroup1.ItemIndex := 0; end; {这是 case 语句比较常规的用法} procedure TForm1.Button1Click(Sender: TObject); begin case RadioGroup1.ItemIndex of 0: Color := clRed; 1: Color := clYellow; 2: Color := clLime; 3: Color := clBlue; end; end; {方法一: 假如要 case 的字符串的长度不同} procedure TForm1.Button2Click(Sender: TObject); var str: string; begin str := RadioGroup1.Items[RadioGroup1.ItemIndex]; case Length(str) of 1 : Color := clRed; 2 : Color := clYellow; 3 : Color := clLime; 4 : Color := clBlue; end; end; {方法二: 假如要 case 的字符串的第一个字母不同, case 是支持字符的} procedure TForm1.Button3Click(Sender: TObject); var str: string; begin str := RadioGroup1.Items[RadioGroup1.ItemIndex]; case str[1] of 'a': Color := clRed; 'b': Color := clYellow; 'c': Color := clLime; 'd': Color := clBlue; end; end; {方法三: 借用 TStringList} procedure TForm1.Button4Click(Sender: TObject); var List: TStringList; str: string; begin List := TStringList.Create; List.Text := RadioGroup1.Items.Text; str := RadioGroup1.Items[RadioGroup1.ItemIndex]; case List.IndexOf(str) of 0: Color := clRed; 1: Color := clYellow; 2: Color := clLime; 3: Color := clBlue; end; List.Free; end; {方法四: 借用枚举} type TMyEnum = (a, bb, ccc, dddd); procedure TForm1.Button5Click(Sender: TObject); var MyEnum: TMyEnum; str: String; begin str := RadioGroup1.Items[RadioGroup1.ItemIndex]; MyEnum := TMyEnum(GetEnumvalue(TypeInfo(TMyEnum), str)); case MyEnum of a : Color := clRed; bb : Color := clYellow; ccc : Color := clLime; dddd : Color := clBlue; end; end; {方法五: 利用对比字符串返回的整数, 这种方法并不太可靠, 但在某种情况下会更灵活} procedure TForm1.Button6Click(Sender: TObject); var str: string; begin str := RadioGroup1.Items[RadioGroup1.ItemIndex]; case CompareStr(str, 'a') of 0: Color := clRed; 1: Color := clYellow; 2: Color := clLime; 3: Color := clBlue; end; end; end.
窗体文件:
object Form1: TForm1 Left = 0 Top = 0 Caption = 'Form1' ClientHeight = 111 ClientWidth = 265 Color = clBtnFace Font.Charset = DEFAULT_CHARSET Font.Color = clWindowText Font.Height = -11 Font.Name = 'Tahoma' Font.Style = [] OldCreateOrder = False Position = poDesktopCenter OnCreate = FormCreate PixelsPerInch = 96 TextHeight = 13 object Button1: TButton Left = 16 Top = 15 Width = 75 Height = 25 Caption = 'Button1' TabOrder = 0 OnClick = Button1Click end object Button2: TButton Left = 97 Top = 15 Width = 75 Height = 25 Caption = 'Button2' TabOrder = 1 OnClick = Button2Click end object Button3: TButton Left = 16 Top = 46 Width = 75 Height = 25 Caption = 'Button3' TabOrder = 2 OnClick = Button3Click end object RadioGroup1: TRadioGroup Left = 178 Top = 8 Width = 80 Height = 94 Caption = 'RadioGroup1' TabOrder = 3 end object Button4: TButton Left = 97 Top = 46 Width = 75 Height = 25 Caption = 'Button4' TabOrder = 4 OnClick = Button4Click end object Button5: TButton Left = 16 Top = 77 Width = 75 Height = 25 Caption = 'Button5' TabOrder = 5 OnClick = Button5Click end object Button6: TButton Left = 97 Top = 77 Width = 75 Height = 25 Caption = 'Button6' TabOrder = 6 OnClick = Button6Click end end