在Ruby 1.8中支持Ruby 1.9的哈希语法 [英] Supporting Ruby 1.9's hash syntax in Ruby 1.8
问题描述
我在整个代码中使用 {key:'value'}
语法来为散列写一个Ruby gem。我的测试全部通过1.9.x,但我(可以理解)在1.8.7中得到语法错误,意外的':',期待')'
。
是否有支持1.8.x的最佳做法?我需要用旧朋友 =>
重写代码,还是有更好的策略? >解决方案
我认为你运气不好,如果你想支持1.8,那么你必须使用 =>
。像往常一样,我会提到你必须在1.9的某些情况下使用 =>
:
- 如果密钥不是符号。请记住,任何对象(符号,字符串,类,浮动,...)都可以成为红宝石哈希中的一个键。
- 如果你需要一个你会引用的符号:
:'this.that'
。 - 如果您使用MongoDB的任何东西,您将使用诸如
:$ set =>散列
但是$ set:散列
是语法错误。
返回我们定期编程的程序。
为什么我说你运气不好?哈希文字的语法(两者都是)在解析器中是硬连线的,我认为你不会有太多的运气从你的宝石中修补解析器。 Ruby 1.8.7's parse.y $ c
assoc:arg_value tASSOC arg_value
{
$$ = list_append(NEW_LIST($ 1),$ 3);
}
;
和 tASSOC
是 =>
因此散列字面值被硬连线为使用 =>
。 1.9.3的说:
assoc:arg_value tASSOC arg_value
{
/ * %%% * /
$$ = list_append(NEW_LIST($ 1 ),$ 3);
/ *%
$$ = dispatch2(assoc_new,$ 1,$ 3);
%* /
}
| tLABEL arg_value
{
/ * %%% * /
$$ = list_append(NEW_LIST(NEW_LIT(ID2SYM($ 1))),$ 2);
/ *%
$$ = dispatch2(assoc_new,$ 1,$ 2);
%* /
}
;
我们再次使用胖箭头语法( arg_value tASSOC arg_value
)和JavaScript风格( tLABEL arg_value
); AFAIK, tLABEL
也是限制什么类型的符号的来源(不是:$ set
,no :'this.that'
,...)可以与JavaScript风格的语法一起使用。当前主干 parse.y
匹配哈希文字的1.9.3。
I'm writing a Ruby gem using the {key: 'value'}
syntax for hashes throughout my code. My tests all pass in 1.9.x, but I (understandably) get syntax error, unexpected ':', expecting ')'
in 1.8.7.
Is there a best practice for supporting the 1.8.x? Do I need to rewrite the code using our old friend =>
, or is there a better strategy?
I think you're out of luck, if you want to support 1.8 then you have to use =>
. As usual, I will mention that you must use =>
in certain cases in 1.9:
- If the key is not a symbol. Remember that any object (symbols, strings, classes, floats, ...) can be a key in a Ruby Hash.
- If you need a symbol that you'd quote:
:'this.that'
. - If you use MongoDB for pretty much anything you'll be using things like
:$set => hash
but$set: hash
is a syntax error.
Back to our regularly scheduled programming.
Why do I say that you're out of luck? The Hash literal syntaxes (both of them) are hard-wired in the parser and I don't think you're going to have much luck patching the parser from your gem. Ruby 1.8.7's parse.y
has this to say:
assoc : arg_value tASSOC arg_value
{
$$ = list_append(NEW_LIST($1), $3);
}
;
and tASSOC
is =>
so hash literals are hard-wired to use =>
. 1.9.3's says this:
assoc : arg_value tASSOC arg_value
{
/*%%%*/
$$ = list_append(NEW_LIST($1), $3);
/*%
$$ = dispatch2(assoc_new, $1, $3);
%*/
}
| tLABEL arg_value
{
/*%%%*/
$$ = list_append(NEW_LIST(NEW_LIT(ID2SYM($1))), $2);
/*%
$$ = dispatch2(assoc_new, $1, $2);
%*/
}
;
We have the fat-arrow syntax again (arg_value tASSOC arg_value
) and the JavaScript style (tLABEL arg_value
); AFAIK, tLABEL
is also the source of the restrictions on what sorts of symbols (no :$set
, no :'this.that'
, ...) can be used with the JavaScript-style syntax. The current trunk parse.y
matches 1.9.3 for Hash literals.
So the Hash literal syntax is hard-wired into the parser and you're stuck with fat arrows if you want to support 1.8.
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