From: Josh Cheek <josh.cheek@...>
Date: 2012-07-25T22:42:10+09:00
Subject: Re: String interpolation / hash of local variables

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On Tue, Jul 24, 2012 at 10:08 PM, Gerbeck Shark <lists@ruby-forum.com>wrote:

> Hello all-
>
> I'm trying to do something likes
>
> Demonstration Ruby/logic
>
> -------
> template = <<-HTML
>  <div>%{example}</div>
>   ...
>  <div>%{foobar}</div>
> HTML
>
> for i in special_list
>      example = ....
>      foobar = ...
>      arr.push template % return_magical_hash_with_local_variables()
> -------
>
> in Python there is a locals() function that returns a dictionary/hash of
> local variables.
>
> In Ruby I've found local_variables() but that does not provide the
> values. It should for just the example above! Or perhaps I can be
> enlightened by someone here?
>
> The other, dirtier idea is something like this:
>
> -------
> template = %q{
>  <div>#{example}</div>
>   ...
>  <div>%{foobar}</div>
> }
>
> for i in special_list
>      example = ....
>      foobar = ...
>      arr.push eval("\"template\"")
> -------
>
> I believe one should avoid calling eval as much as possible. I tried the
> "Facets" package,
> "String.interpolate{template}" calls eval, it just masks the fact.
>
> This could be avoided if there were a function that return a dictionary
> or hash of local variables.
>
> --
> Posted via http://www.ruby-forum.com/.
>
>
There is a templating library in the stdlib called erb (
http://rdoc.info/stdlib/erb/ERB)


require 'erb'

template = <<-HTML
 <div><%= example %></div>
 <div><%= foobar  %></div>
HTML

# ===== simple example with toplevel locals =====
example = 'EXAMPLE'
foobar = 'FOOBAR'
ERB.new(template).result binding # => " <div>EXAMPLE</div>\n
<div>FOOBAR</div>\n"


# ===== more realistic example with methods on an object =====
# you can technically do ivars in these, too, which
# is what most web frameworks use, but that sucks IMO
class MyTemplateRenderer
  attr_accessor :example, :foobar

  def initialize(example, foobar)
    self.example, self.foobar = example, foobar
  end

  def render(template)
    ERB.new(template).result binding
  end
end

renderer = MyTemplateRenderer.new 'ExAmPlE', 'FoObAr'
renderer.render template # => " <div>ExAmPlE</div>\n <div>FoObAr</div>\n"

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<div class=3D"gmail_quote">On Tue, Jul 24, 2012 at 10:08 PM, Gerbeck Shark =
<span dir=3D"ltr">&lt;<a href=3D"mailto:lists@ruby-forum.com" target=3D"_bl=
ank">lists@ruby-forum.com</a>&gt;</span> wrote:<br><blockquote class=3D"gma=
il_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-lef=
t:1ex">
Hello all-<br>
<br>
I&#39;m trying to do something likes<br>
<br>
Demonstration Ruby/logic<br>
<br>
-------<br>
template =3D &lt;&lt;-HTML<br>
=A0&lt;div&gt;%{example}&lt;/div&gt;<br>
=A0 ...<br>
=A0&lt;div&gt;%{foobar}&lt;/div&gt;<br>
HTML<br>
<br>
for i in special_list<br>
=A0 =A0 =A0example =3D ....<br>
=A0 =A0 =A0foobar =3D ...<br>
=A0 =A0 =A0arr.push template % return_magical_hash_with_local_variables()<b=
r>
-------<br>
<br>
in Python there is a locals() function that returns a dictionary/hash of<br=
>
local variables.<br>
<br>
In Ruby I&#39;ve found local_variables() but that does not provide the<br>
values. It should for just the example above! Or perhaps I can be<br>
enlightened by someone here?<br>
<br>
The other, dirtier idea is something like this:<br>
<br>
-------<br>
template =3D %q{<br>
=A0&lt;div&gt;#{example}&lt;/div&gt;<br>
=A0 ...<br>
=A0&lt;div&gt;%{foobar}&lt;/div&gt;<br>
}<br>
<br>
for i in special_list<br>
=A0 =A0 =A0example =3D ....<br>
=A0 =A0 =A0foobar =3D ...<br>
=A0 =A0 =A0arr.push eval(&quot;\&quot;template\&quot;&quot;)<br>
-------<br>
<br>
I believe one should avoid calling eval as much as possible. I tried the<br=
>
&quot;Facets&quot; package,<br>
&quot;String.interpolate{template}&quot; calls eval, it just masks the fact=
.<br>
<br>
This could be avoided if there were a function that return a dictionary<br>
or hash of local variables.<br>
<span class=3D"HOEnZb"><font color=3D"#888888"><br>
--<br>
Posted via <a href=3D"http://www.ruby-forum.com/" target=3D"_blank">http://=
www.ruby-forum.com/</a>.<br>
<br>
</font></span></blockquote></div><br><div>There is a templating library in =
the stdlib called erb (<a href=3D"http://rdoc.info/stdlib/erb/ERB">http://r=
doc.info/stdlib/erb/ERB</a>)</div><div><br></div><div><br></div><div><div>
require &#39;erb&#39;</div><div><br></div><div>template =3D &lt;&lt;-HTML</=
div><div>=A0&lt;div&gt;&lt;%=3D example %&gt;&lt;/div&gt;</div><div>=A0&lt;=
div&gt;&lt;%=3D foobar =A0%&gt;&lt;/div&gt;</div><div>HTML</div><div><br></=
div><div>
# =3D=3D=3D=3D=3D simple example with toplevel locals =3D=3D=3D=3D=3D</div>=
<div>example =3D &#39;EXAMPLE&#39;</div><div>foobar =3D &#39;FOOBAR&#39;</d=
iv><div>ERB.new(template).result binding # =3D&gt; &quot; &lt;div&gt;EXAMPL=
E&lt;/div&gt;\n &lt;div&gt;FOOBAR&lt;/div&gt;\n&quot;</div>
<div><br></div><div><br></div><div># =3D=3D=3D=3D=3D more realistic example=
 with methods on an object =3D=3D=3D=3D=3D</div><div># you can technically =
do ivars in these, too, which</div><div># is what most web frameworks use, =
but that sucks IMO</div>
<div>class MyTemplateRenderer</div><div>=A0 attr_accessor :example, :foobar=
</div><div>=A0=A0</div><div>=A0 def initialize(example, foobar)</div><div>=
=A0 =A0 self.example, self.foobar =3D example, foobar</div><div>=A0 end</di=
v><div>=A0=A0</div>
<div>=A0 def render(template)</div><div>=A0 =A0 ERB.new(template).result bi=
nding</div><div>=A0 end</div><div>end</div><div><br></div><div>renderer =3D=
 MyTemplateRenderer.new &#39;ExAmPlE&#39;, &#39;FoObAr&#39;</div><div>rende=
rer.render template # =3D&gt; &quot; &lt;div&gt;ExAmPlE&lt;/div&gt;\n &lt;d=
iv&gt;FoObAr&lt;/div&gt;\n&quot;</div>
<div><br></div></div>

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