基本知識1--常量與變量的聲明與作用域

                                              常量與變量的聲明與作用域

    一,常量

              1,在delphi中常量生命的方法如下

                                   (1) const myconst=value;

                                   (2) const myconst:mytype=value;

             2,作用域

                                  (1)  全局常量，可被其他unit 引用。定義在interface與implementation之間

                                  (2) 單元常量，本單元內可見。定義在implementation裏

                                  (3)局部常量，在一段過程或函數內可見。定義在該函數或過程內。

 

                       eg:

                                                        unit myunit;

                                                          interface  

                                                             uses calss,dialogs;

                                                          const

  myconst1:string='myconst1string';//全局常量(或myconst1='myconst1string')

                                                       type

                                                              tform1=class(tform);

                                                      public

                                                             procedure myprocedure(sender:tobject);

                                                          end;

                                                  implementation

                        const   myconst2='myconst2strinng'//單元常量

                                            procedure tform1.myprocedure(sender:tobject);

                                              const    myconst3='myconst3string' ;//局域常量

                                                       begin

                                                      end;

    二，變量

                定義

                      1 var  myvar:string;  

                      2 var myvar:string='myvar';//變量不可以直接var myvar='myvar'

              作用域與常量一樣