Local functions and processes

The functions and processes defined in functions and processes are called local functions and processes (subprograms). subprograms are only valid within the parent process.

Next, let's take a look at how to implement the definition and use of a local function and process.

1,CreateApplication.

2,InForm1PlaceMemoComponent (Memo1) And twoButtonComponent (Button1AndButton2).

3,Double-clickButton1Button inButton1clickEnter the following code in the event:

procedure TForm1.Button1Click(Sender: TObject);var  X: Integer;  {a local procedure}  procedure Test;  begin    Memo1.Lines.Add('Local Function, X = ' + IntToStr(X));  end;begin  X := 100;  Memo1.Lines.Clear;  Memo1.Lines.Add('Main Function, X = ' + IntToStr(X));  Test;end;

4,Double-clickButton2Button inButton2clickEnter the following code in the event:

Procedure tform1.button2click (Sender: tobject); begin test; {because test is defined in button1click, an error is returned.} end;

5,PressCTRL + F9Compile the project and report the following error:Undeclared identifier: 'test'(Undefined identifier)

6,Comment outButton2clickInTestCall the process, re-compile and run, and clickButton1The result is as follows:

Analysis

• The test process is included in the VaR segment of the button1click process. The process declared using this method is a local process, and it is limited to the functions and processes that contain it. A local subroutine can only be called by routines that contain it, but cannot be called in other places of the program. Therefore, test cannot be called during the button2click process.
• An important property of a local process and function is that the variables contained in the process and function are also valid in the local subroutine. The values of the two X variables shown in the preceding example in memo1 are both 100, it indicates that the X variable is not only available in button1click, but can also be used in its subprocess test.

All the above programs are compiled in Delphi7. sample code is downloaded: Local program and process .rar