Use strings in case statements

Unfortunately, the case statement of Delphi does not support strings, but I think this may also be based on efficiency considerations;
If you want to use a string in case, it is not an alternative. Five methods are provided here.
In this example:

Code file:

Unit unit1; interfaceuses 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 transaction (Sender: tobject ); procedure extract (Sender: tobject); Procedure button3click (Sender: tobject); Procedure extract (Sender: tobject ); end; var form1: tform1; implementation {$ R *. DFM} uses typinfo; {operation enumeration use} {initialize a single-choice group for testing} procedure tform1.formcreate (Sender: tobject); begin radiogroup1.items. commatext: = 'a, BB, CCC, dddddd'; radiogroup1.itemindex: = 0; end; {This is a common case statement} procedure tform1.button1click (Sender: tobject ); begin case radiogroup1.itemindex of 0: Color: = clred; 1: Color: = clyellow; 2: Color: = cllime; 3: Color: = clblue; end; {Method 1: suppose the length of the string to be case is different} 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; {Method 2: if the first letter of the string to be case is different, case supports characters} 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; {method 3: Borrow 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; {Method 4: Borrow enumeration} 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; {Method 5: Compare the integers returned by a string. This method is not very reliable, but in some cases it will be more flexible} 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.
 

Form file:

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  endend