Editing Object REXX (section)

=== Message paradigm ===
Similar to the messaging paradigm implemented by [[Alan Kay]] in Smalltalk, everything in ooRexx is an object that can be communicated with. The notion of sending messages to objects as if they were living beings helps beginners to learn OOP concepts.<ref name=":4">{{Cite journal |last1=Flatscher |first1=Rony G. |last2=Winkler |first2=Till |title=Employing the Message Paradigm to Ease Learning Object-oriented Concepts and Programming |url=https://research.wu.ac.at/files/64505159/mipro24_9194_Flatscher_Winkler_EmployingMessageParadigm_final-4.pdf |journal=In 2024 47th MIPRO ICT and Electronics Convention (MIPRO) |pages=1244–1249}}</ref> In contrast to Smalltalk, there is an explicit message operator, the tilde (<code>~</code>), where the receiving object is placed to the left of it and the result of the operation is returned. Sending a message leads to the activation of a method with the corresponding method name and to the manipulation of the receiving object. Like Smalltallk, ooRexx messages can be cascaded if two tildes (<code>~~</code>) are used instead of one, returning the object that received the method rather than the result produced.<ref name=":9">{{Cite book |last1=Ashley |first1=W. David |url=https://sourceforge.net/projects/oorexx/files/oorexx-docs/5.0.0/rexxpg.pdf |title=ooRexx Documentation 5.0.0 Programmer Guide |last2=Flatscher |first2=Rony G. |last3=Hessling |first3=Mark |last4=McGuire |first4=Rick |last5=Peedin |first5=Lee |last6=Sims |first6=Oliver |last7=Wolfers |first7=Jon |date=2022 |publisher=RexxLA}}</ref>

The default behavior of most methods can be changed by specifying an option, which can be either spelled out or abbreviated and is not case-sensitive. When reading code, this enables a literal understanding and reduces the learning effort for beginners, as there is no need to learn the meaning of abbreviations.<ref name=":3" /> For example, the method with the name <code>strip</code> removes leading and trailing blanks by default. This behavior can be changed, for example, by specifying <code>"leading"</code> or <code>"l"</code> as an option. While functions are nested in classic Rexx, messages can be chained in ooRexx, which improves the readability of a [[Statement (computer science)|statement]].<ref name=":4" /><syntaxhighlight lang="oorexx" style="background-color: #ffffff; !important" line="1">
a = "   I am ooRexx!"
say a                           /* output:    I am ooRexx! */
say a~Strip("Leading")          /* output: I am ooRexx!    */
say a~strip("l")~reverse        /* output: !xxeRoo ma I    */
</syntaxhighlight>