How do I concisely check whether a string equals any of several values?

3
votes

I currently have one record (with various values) and three user constants with specific assigned values (e.g. names, etc.).

I can compare an edit box against one user like this:

if edit1.text = user1 
 then xxxx

This is all well, but how do I specify that the edit box must check between the three different users?

Example:

if edit1.text = user1 to user3
 then xxxx

How Do I go about doing this?

4
delphi
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4 Answers

9
votes

Recent versions of Delphi (I use XE) have unit StrUtils.pas which contains

function MatchText(const AText: string; const AValues: array of string): Boolean;
function MatchStr(const AText: string; const AValues: array of string): Boolean;

MatchStr is the case sensitive version.

Your problem can now be solved like this:

if MatchStr(edit1.text, [user1, user2, user3])
  then xxxx
3
votes

You can use AnsiMatchStr()/AnsiMatchText() to check if a string matches one of the string in an array. AnsiIndexStr()/AnsiIndexText() also return the index of the matched string, and thereby can be useful in case of statements.

2
votes

For a set which might grow later at runtime, I might declare a TStringList, if I have a class instance to hold the "acceptable values" and replace the large if (x=a1) or (x=a2) or (x=a3).... sequence with:

 // FAcceptableValues is TStringList I set up elsewhere, such as my class constructor.
 if FAcceptableValues.IndexOf(x)>=0 then ...

That has the benefit of being customizeable. In the case of your logic, I would consider making a list of controls, and doing a Match function:

 var 
   Users:TList<TUser>;
   Edits:TList<TEdit>;
 begin
    ... other stuff like setup of FUsers/FEdits.
    if Match(Users,Edits) then ...

Match could be written as a simple for next loop:

 For U in Users do 
     for E in Edits do
          if U.Text=E.Text then 
            begin 
             result := true;
             exit
            end;
1
votes

Delphi doesn't support the use of strings in case statements so you have to do it the hard way.

 if ((user1.name = edit1.text) and (user1.surname = edit2.text)) or 
    ((user2.name = edit1.text) and (user2.surname = edit2.text)) or 
    ((user3.name = edit1.text) and (user3.surname = edit2.text)) 
   then xxxx