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From: Paolo Di Tommaso <paolo.ditommaso@gmail.com>
Date: Thu, 26 May 2016 23:52:20 +0200
Message-ID: <CADgKzdyn0s4MD6_C9fc6oPN7KABNOfhesTwY-gXD-dUb=5HPwA@mail.gmail.com>
Subject: Re: List and GString
To: users@groovy.apache.org
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archived-at: Thu, 26 May 2016 21:53:05 -0000

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Looking in the GString implementation I noticed that it call the
InvokeHelper.write
<https://github.com/apache/groovy/blob/master/src/main/org/codehaus/groovy/=
runtime/InvokerHelper.java#L500>
method.

I've tried implementing a DelegatingMetaClass
<https://objectpartners.com/2013/07/30/customizing-mop-in-groovy/> but it
does not work. At the end of the day it should to be possible to use
meta-programming to override Java compiled code.

Maybe the trick you are mentioning is ExpondoMetaClass.enableGlobally
<http://docs.groovy-lang.org/latest/html/api/groovy/lang/ExpandoMetaClass.h=
tml#enableGlobally%28%29>
?


Is there any other possible workaround ?


Cheers,
Paolo


On Thu, May 26, 2016 at 11:02 PM, Emmanuel Rosa <goaway1000@gmail.com>
wrote:

> The rendering is actually produced by InvokerHelper:
> https://github.com/apache/groovy/blob/master/src/main/org/codehaus/groovy=
/runtime/InvokerHelper.java#L123
>
> I tried overriding it with a category and also via the metaClass, but
> neither worked. I recall some kind of trick that=E2=80=99s needed when us=
ing the
> metaClass with some classes, to get it to take, but I don=E2=80=99t remem=
ber the
> details. :(
>
> On May 26, 2016, at 2:06 PM, Paolo Di Tommaso <paolo.ditommaso@gmail.com>
> wrote:
>
> Dear all,
>
> I have a use case in which I need to override the `toString` method of a
> custom List class and use it when interpolating that list object in a
> GString.
>
> It turns out the Groovy uses its own formatting methods for List and othe=
r
> structures, so the my custom `toString` is simply ignored.
>
> To explain it better take in consideration this example:
>
> class MyList extends ArrayList {
>
>   String toString() {
>     this.join('-')
>   }
>
> }
>
>
> def x =3D new MyList()
> x << 1 << 2 << 3
>
> assert x.toString() =3D=3D '1-2-3'
> assert "$x" =3D=3D '1-2-3'
>
> Assertion failed:
> assert "$x" =3D=3D '1-2-3'
>          |  |
>          |  false
>          [1, 2, 3]
>
> The second assertion fails for the reason said above. Now I'm wondering i=
t
> there's any way to override somehow the GString default rendering mechani=
sm
> in such a way I can inject my own formatting rule for my custom class.
>
> Any suggestion is appreciated.
>
>
>
> Cheers,
> Paolo
>
>
>
>
>

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<div dir=3D"ltr">Looking in the GString implementation I noticed that it ca=
ll the <a href=3D"https://github.com/apache/groovy/blob/master/src/main/org=
/codehaus/groovy/runtime/InvokerHelper.java#L500">InvokeHelper.write</a> me=
thod.=C2=A0<div><br></div><div>I&#39;ve tried implementing a <a href=3D"htt=
ps://objectpartners.com/2013/07/30/customizing-mop-in-groovy/">DelegatingMe=
taClass</a>=C2=A0but it does not work. At the end of the day it should to b=
e possible to use meta-programming to override Java compiled code.</div><di=
v><br></div><div>Maybe the trick you are mentioning is <a href=3D"http://do=
cs.groovy-lang.org/latest/html/api/groovy/lang/ExpandoMetaClass.html#enable=
Globally%28%29">ExpondoMetaClass.enableGlobally</a> ?</div><div><br></div><=
div><br></div><div>Is there any other possible workaround ?=C2=A0</div><div=
><br></div><div><br></div><div>Cheers,</div><div>Paolo</div><div><br></div>=
</div><div class=3D"gmail_extra"><br><div class=3D"gmail_quote">On Thu, May=
 26, 2016 at 11:02 PM, Emmanuel Rosa <span dir=3D"ltr">&lt;<a href=3D"mailt=
o:goaway1000@gmail.com" target=3D"_blank">goaway1000@gmail.com</a>&gt;</spa=
n> wrote:<br><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;b=
order-left:1px #ccc solid;padding-left:1ex"><div style=3D"word-wrap:break-w=
ord">The rendering is actually produced by InvokerHelper:=C2=A0<a href=3D"h=
ttps://github.com/apache/groovy/blob/master/src/main/org/codehaus/groovy/ru=
ntime/InvokerHelper.java#L123" target=3D"_blank">https://github.com/apache/=
groovy/blob/master/src/main/org/codehaus/groovy/runtime/InvokerHelper.java#=
L123</a><div><br></div><div>I tried overriding it with a category and also =
via the metaClass, but neither worked. I recall some kind of trick that=E2=
=80=99s needed when using the metaClass with some classes, to get it to tak=
e, but I don=E2=80=99t remember the details. :(</div><div><div class=3D"h5"=
><div><br><div><blockquote type=3D"cite"><div>On May 26, 2016, at 2:06 PM, =
Paolo Di Tommaso &lt;<a href=3D"mailto:paolo.ditommaso@gmail.com" target=3D=
"_blank">paolo.ditommaso@gmail.com</a>&gt; wrote:</div><br><div><div dir=3D=
"ltr">Dear all,=C2=A0<div><br></div><div>I have a use case in which I need =
to override the `toString` method of a custom List class and use it when in=
terpolating that list object in a GString.=C2=A0</div><div><br></div><div>I=
t turns out the Groovy uses its own formatting methods for List and other s=
tructures, so the my custom `toString` is simply ignored.=C2=A0</div><div><=
br></div><div>To explain it better take in consideration this example:=C2=
=A0</div><div><div><br></div><div><font face=3D"monospace, monospace">class=
 MyList extends ArrayList {</font></div><div><font face=3D"monospace, monos=
pace"><br></font></div><div><font face=3D"monospace, monospace">=C2=A0 Stri=
ng toString() {</font></div><div><font face=3D"monospace, monospace">=C2=A0=
 =C2=A0 this.join(&#39;-&#39;)</font></div><div><font face=3D"monospace, mo=
nospace">=C2=A0 }</font></div><div><font face=3D"monospace, monospace"><br>=
</font></div><div><font face=3D"monospace, monospace">}</font></div><div><f=
ont face=3D"monospace, monospace"><br></font></div><div><font face=3D"monos=
pace, monospace"><br></font></div><div><font face=3D"monospace, monospace">=
def x =3D new MyList()</font></div><div><font face=3D"monospace, monospace"=
>x &lt;&lt; 1 &lt;&lt; 2 &lt;&lt; 3=C2=A0</font></div><div><font face=3D"mo=
nospace, monospace"><br></font></div><div><font face=3D"monospace, monospac=
e">assert x.toString() =3D=3D &#39;1-2-3&#39;</font></div><div><font face=
=3D"monospace, monospace">assert &quot;$x&quot; =3D=3D &#39;1-2-3&#39;</fon=
t></div><div><font face=3D"monospace, monospace"><br></font></div><div><fon=
t face=3D"monospace, monospace">Assertion failed:=C2=A0</font></div><div><f=
ont face=3D"monospace, monospace">assert &quot;$x&quot; =3D=3D &#39;1-2-3&#=
39;</font></div><div><font face=3D"monospace, monospace">=C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0| =C2=A0|</font></div><div><font face=3D"monospace, monosp=
ace">=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0| =C2=A0false</font></div><div><font=
 face=3D"monospace, monospace">=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0[1, 2, 3]<=
/font></div></div><div><br></div><div>The second assertion fails for the re=
ason said above. Now I&#39;m wondering it there&#39;s any way to override s=
omehow the GString default rendering mechanism in such a way I can inject m=
y own formatting rule for my custom class.=C2=A0</div><div><br></div><div>A=
ny suggestion is appreciated.=C2=A0</div><div><br></div><div><br></div><div=
><br></div><div>Cheers,</div><div>Paolo</div><div><br></div><div><br></div>=
<div><br></div></div>
</div></blockquote></div><br></div></div></div></div></blockquote></div><br=
></div>

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