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

我正在使用 {key: 'value'} 语法为整个代码中的散列编写一个 Ruby gem.我的测试都在 1.9.x 中通过，但我(可以理解)在 1.8.7 中得到 syntax error, unexpected ':', expecting ')'.

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.

是否有支持 1.8.x 的最佳实践?我是否需要使用我们的老朋友 => 重写代码，或者有更好的策略吗?

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?

推荐答案

我觉得你运气不好，如果你想支持 1.8 那么你必须使用 =>.像往常一样，我会提到在 1.9 的某些情况下必须使用 =>:

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:

1. 如果键不是符号.请记住，任何对象(符号、字符串、类、浮点数等)都可以作为 Ruby Hash 中的键.
2. 如果您需要引用的符号::'this.that'.
3. 如果您将 MongoDB 用于几乎任何事情，您将使用诸如 :$set => 之类的东西.hash 但 $set: hash 是一个语法错误.

1. If the key is not a symbol. Remember that any object (symbols, strings, classes, floats, ...) can be a key in a Ruby Hash.
2. If you need a symbol that you'd quote: :'this.that'.
3. If you use MongoDB for pretty much anything you'll be using things like :$set => hash but $set: hash is a syntax error.

回到我们定期安排的节目.

Back to our regularly scheduled programming.

为什么我说你不走运?Hash 文字语法(两者)在解析器中是硬连接的，我认为从 gem 修补解析器不会有太多运气.Ruby 1.8.7 的 parse.y 有话要说:

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);
             }
         ;

和 tASSOC 是 => 所以散列文字是硬连线的以使用 =>.1.9.3's 是这样说的:

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);
             %*/
             }
         ;

我们再次使用粗箭头语法(arg_value tASSOC arg_value)和 JavaScript 样式(tLABEL arg_value)；AFAIK，tLABEL 也是限制符号种类的来源(没有 :$set，没有 :'this.that'，...) 可以与 JavaScript 风格的语法一起使用.当前主干 parse.y 匹配 1.9.3 的哈希文字.

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.

所以 Hash 文字语法被硬连接到解析器中，如果你想支持 1.8，你就会被粗箭头所困.

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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