bcquality/microsoft/knowledge/style/this-keyword-in-codeunits.md

bc-version	domain	keywords	technologies	countries	application-area
25..	style	this codeunit self-reference aa0248 scope	al	w1	all

Use the this keyword for self-reference inside codeunits (CodeCop AA0248)

Description

CodeCop AA0248 recommends prefixing self-references inside a codeunit with this. this.ValidateCustomer(Customer) is unambiguous: the call resolves to a procedure on the current codeunit, not to a local variable or a procedure on a passed-in object. Without the prefix, a reader of a 200-line procedure has to scan the whole codeunit to confirm whether ValidateCustomer is local. this also makes it possible to pass the current codeunit as an argument — SomeOtherCodeunit.DoWork(this) — which is the only way to expose the running codeunit instance to a collaborator. The rule applies only to codeunits, not to pages, reports, queries, or tables — those object types do not have a this reference in AL.

Best Practice

Inside a codeunit, prefix calls to procedures and accesses to global variables on the same codeunit with this., and pass this when an external codeunit needs a reference to the running instance.

See sample: this-keyword-in-codeunits.good.al.

Anti Pattern

Calling a codeunit-local procedure as a bare identifier (ValidateCustomer(Customer)) when other readings are possible. The ambiguity costs reading time on every encounter and grows with codeunit size.

See sample: this-keyword-in-codeunits.bad.al.