[
https://issues.apache.org/jira/browse/GROOVY-11059?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17722866#comment-17722866
]
Eric Milles edited comment on GROOVY-11059 at 5/15/23 5:49 PM:
---------------------------------------------------------------
Groovy constructor shorthand syntax is available:
{code:groovy}
class MyClass {
MyClass(String s) {
// ...
}
}
MyClass anObject = ["SomeString"]
{code}
"def anObject = 'SomeString' as MyClass" requires String/CharSequence/...
{{asType(MyClass)}}, which you could supply just to your block with "use":
{code:groovy}
class Cat {
static <T> T asType(String string, Class<T> type) {
if (type == MyClass) {
return new MyClass(string)
} else { // continue cast as type:
StringGroovyMethods.asType(string, type)
}
}
}
use (Cat) {
def obj = 'foobar' as MyClass
print obj
}
{code}
You can add "equals(Object)" or "compareTo(String)" to MyClass to support "mc
== 'str'". And "'str' == mc" by adding the reverse to Cat; be sure to delegate
to the default groovy method for other RHS types if you want "'str' == number"
to still work in your use block.
Implicit conversion like "MyClass mc = 'str'" or "mc == 'str'" is a slippery
slope. There is no general mechanism for introducing new conversions. Is this
what your request is?
was (Author: emilles):
Groovy constructor shorthand syntax is available:
{code:groovy}
class MyClass {
MyClass(String s) {
// ...
}
}
MyClass anObject = ["SomeString"]
{code}
"def anObject = 'SomeString' as MyClass" requires String/CharSequence/...
{{asType(MyClass)}}, which you could supply just to your block with "use":
{code:groovy}
class Cat {
static <T> T asType(String string, Class<T> type) {
if (type == MyClass) {
return new MyClass(string)
} else { // continue cast as type:
StringGroovyMethods.asType(string, type)
}
}
}
use (Cat) {
def obj = 'foobar' as MyClass
print obj
}
{code}
You can add "equals(String)" or "compareTo(String)" to MyClass to support "mc
== 'str'". And "'str' == mc" by adding the reverse to Cat; be sure to delegate
to the default groovy method for other RHS types if you want "'str' == number"
to still work in your use block.
Implicit conversion like "MyClass mc = 'str'" or "mc == 'str'" is a slippery
slope. There is no general mechanism for introducing new conversions. Is this
what your request is?
> 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") {...{}}}}
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
