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IsMatch() show allow for variable (not constant) regular expressions

IsMatch() should allow the ability to use a variable (global and context) for the Pattern parameter (2nd) that contains the regular expression pattern.   Currently IsMatch() function requires the regular expression (2nd parameter) to be a constant value (literal string).

 

ie: the request is that the below should be permissible:

 

Set( URL_MATCH, "(ht|f)tp(s?)://[0-9a-zA-Z]([-.\w]*[0-9a-zA-Z])*(:(0-9)*)*(/?)([a-zA-Z0-9-.?,'/\+&%$#_]*)?" );

Set( IsUrl, IsMatch( TextInput1.Text, URL_MATCH ) )

(Note the forum here converts part of the regular expression in the code section above into a frown face, whereas that section really should be a colon : followed by a left paren ( - the expression I attempted to put here is the same in IsMatch() for identifying a URL)

 

Currently, this results in the error:

 

   The function 'IsMatch' has some invalid arguments.

   Regular expressions must be constant values.

 

Why must this be constant?  Seems that this is an unnecessary limitation.

 

Issues with this approach (requiring these to be constant) include:

 

  1. Inability to define the RegEx expresions in a single place in the code (setting in a global variable) and use throughout the application (probably issue #1 overall with PowerApps is limitations on code reuse and having to duplicate unnecessarily code).  Currently I have to copy IsMatch() expressions throughout my code with the SAME literal string everywhere (of course this could be helped if we had Macro support in PowerApps...)"

  2. Inability to read RegEx expressions from an external source - ie: assume the requirement is to allow the expression to be changed external to the application, and the application (on startup) read these in.  This is a realistic requirement.

 

Please consider modifying IsMatch() to allow the "Pattern" parameter to be a string.  

 

Note that since PowerApps does not have true definable constants, the only way to do this is with a literal string, ie: 

   "(ht|f)tp(s?)://[0-9a-zA-Z]([-.\w]*[0-9a-zA-Z])*(:(0-9)*)*(/?)([a-zA-Z0-9-.?,'/\+&%$#_]*)?"


which does not promote code reusability - and thus the only way to use IsMatch() is with a literal string.

 

However, even with support for true contants or macros - neither of which are available in PowerApps (which may be one way to address #1), issue #2 is still not addressed.  

 

Allowing for a variable to be used for Pattern would not only promote code reusability to some degree (#1 - since I could just set my patterns in variables early in the code like in OnStart()), but also allow for much more maintainable applications and more flexibility and address #2.

 

BTW - also note that the documentation does NOT address this limitation of IsMatch() (ie: that Pattern must be a constant)

Status: Under Review

Upgrading to In Review, adding @LanceDelano and @GregLi who are looking at improvements in this area

Comments
Anonymous
Not applicable

This should really be possible

JR-BejeweledOne
Super User

I have to really stress this.   As a comparison operator, IsMatch should take a variable input, otherwise its uses are very limited.  To make it a truly valuable comparison operator it needs to be able to be used with a variable in addition to the static patterns.

Ianbudson
Frequent Visitor

I just came across this limitation and am now stumped on an app.......why can't it use a variable?????

GavinM
Advocate I

Just working on a forms and workflow app that uses metadata to build the form.  I thought that using a flexible regex would be a great way to validate data ... amazed to find that it had to be a literal string!

 

Is anything being done on this?  IsMatch not being able to take a variable for the pattern really limits its capability.