4.15.2013 Simple text search

Searching is one of the tasks of programing that reduces so much of our work and hardship. Today we see a very simple string search sample code...

For second variation/update of this program see this article.

Text search is very easy through a function named PosEx from the strutils unit. The function is given a substring (which part we want to search) and a string (which is the whole text in which we search).

There are many syntax. We would need this syntax:

function PosEx(

  const SubStr: ;

  const S:

):Integer;

You can test this function with a code like this:

Ret = PosEx('pet', 'I have a big pet dinosaur');

Ret would return 14, as the text 'pet' is found on 14th position of the given string.

Quick Tutorial

Create a new Application Project. Project->New Project->Application->OK.
Create a TMemo, a TEdit, and a TButton. Select the memo and set its Scrollbars to ssAutoVertical.
Add strutils to the uses clause:

uses
..., strutils;

Double click the button and write the following code:

var

  findpos: integer;

begin

  // find the occurance of the text

  findpos := PosEx(Edit1.Text, Memo1.Text);



  // we start our selection

  Memo1.SelStart := findpos - 1;

  // we set the length of our selection

  Memo1.SelLength := Length(Edit1.Text);



  // we set focus to memo to show the selection to

  // the user

  Memo1.SetFocus;

end;

Explanation

Memo1.SelStart := findpos - 1;

SelStart is 0-based (starts from 0). PosEx on the other hand is 1-based (starts from 1). So findpos is 1-based. We -1 from findpos to make it zero-based, for SelStart.

Run It

Go to Run->Run. Write something in the memo and then write something in the editbox then click the button.

Download sample source zip

Download sample source code zip from here: http://db.tt/dMCf7Zku
Or here: http://bit.ly/105spbe

Size: 636 KB
The zip file contains the executable EXE file.