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https://issues.apache.org/jira/browse/GROOVY-11059?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17723123#comment-17723123
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Jim Klimov commented on GROOVY-11059:
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At least looking at our codebase - yes, there are a number of "legacy"
assignments from magic strings into what now would be proper purpose-made class
objects, which would be easier to keep "as is" while we refactor stuff, which
can take months (not a high prio).
With current Groovy, if {{anObject}} is declared via plain {{{}def{}}}, it
would become a {{String}} after such assignment and forget about
{{{}MyClass{}}}; if it is declared with specific type, we would currently get
base Java cast exceptions upon those assignments, unless we spell out {{as
MyClass}} all over the codebase (and/or {{use(someCategory)}} wherever we do
this – which we would often discover retroactively as some build/test/publish
pipeline crashes mid-flight with a stack trace.
On a side note, regarding some common method generally to cast from arbitrary
other types: there is precedent in many JDK classes and online articles with
generic {{of()}} or {{valueOf()}} methods in some interface/class inheritance
trees (collections, enums...) and specific {{fromString()}} etc. prevalent in
online examples but I don't think being present in any major SDK. I guess the
root nit here is that as JDK historically defined an {{Object::equals()}}
method, they should have made some {{Object::valueOf()}} (which could well cast
an exception by default and be implemented by whoever cares for whatever
use-cases) and be done with this subject across the board.
> Want a way to define casting/coercing FROM other classes as part of my class
> ----------------------------------------------------------------------------
>
> Key: GROOVY-11059
> URL: https://issues.apache.org/jira/browse/GROOVY-11059
> Project: Groovy
> Issue Type: Wish
> Reporter: Jim Klimov
> Priority: Major
>
> Java has basic casting which relies on one object having a class/interface
> which is descendant of another in the equation. Groovy extends this with
> coercion which relies on the origin class defining an {{asType()}} method to
> state how convert it into an instance of a target class.
> For example, if I want to assign my class from a standard {{String}} I'd have
> to hack with metaclass of String to extend its {{asType}} to recognize
> {{MyClass}} and coerce INTO it, and then I'd be able to say:
> {code:java}
> MyClass myval = "SomeString" as MyClass{code}
> This is clumsy both on implementation side (hacking into other people's code
> is not too portable, and has complications with code that runs this hack many
> times like a Jenkins Shared Library that would change server JVM's String
> over and over for each run), and on coding side (while "as SomeClass" is
> explicit, someone has to write it which adds noise in refactorings and goes
> against the type simplicity trend of the language).
> My proposal is to support a common optional method everywhere, in the
> groovyish manner of plastering so many other optional operator overloads like
> {{{}asType(){}}}, {{{}isCase(){}}}, {{plus()}} et al, which would be
> effectively an inverse {{asType()}} and overload the assignment operator.
> By default it could invoke single-parameter constructors (e.g. if I define a
> {{MyClass(String)}} one - that can be used to cast the assignment from a
> {{{}String{}}}), and it might be extensible if someone has more complex ideas
> for their class (e.g. change something in the existing instance instead of
> creating a new one, if the override is non-static, or if it generally gets a
> parameter with an instance of this class and this parameter is null or not).
> Either way, for script writers it would be just a simple assignment symbol
> with smarts behind the curtain.
> Possibly this might fill in the gap of current {{equals()}} overload that did
> not always work well for me (possibly due to ancient groovy in Jenkins core)
> to check {{{}if (myClassVal == "somestring") {...{}}}}
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