Ruby 大括号块语法在 do...end 时不起作用

Question

我正在使用 this gem。当我使用以下语法时，它工作正常：

every :day do
  rake 'billing:daily'
end

但是，当我使用以下语法时，gem 给我语法错误：

every :day { rake 'billing:daily' }

输出：

~/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/whenever-0.10.0/lib/whenever/job_list.rb:25:in `instance_eval': config/schedule.rb:26: syntax error, unexpected '{', expecting end-of-input (SyntaxError)
every :day { rake 'billing:daily' }
            ^
    from ~/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/whenever-0.10.0/lib/whenever/job_list.rb:25:in `initialize'
    from ~/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/whenever-0.10.0/lib/whenever.rb:12:in `new'
    from ~/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/whenever-0.10.0/lib/whenever.rb:12:in `cron'
    from ~/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/whenever-0.10.0/lib/whenever/command_line.rb:42:in `run'
    from ~/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/whenever-0.10.0/lib/whenever/command_line.rb:6:in `execute'
    from ~/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/whenever-0.10.0/bin/whenever:44:in `<top (required)>'
    from ~/.rbenv/versions/2.4.3/bin/whenever:23:in `load'
    from ~/.rbenv/versions/2.4.3/bin/whenever:23:in `<main>'

两者不是一回事吗？为什么前者有效而后者无效？

Answer 1

这是一个 parsing/precedence 问题。大括号尝试绑定到最近的标记，在本例中为 :day，但您希望它绑定到 every()。您必须编写 every(:day) { rake 'billing:daily' } 以将其显式绑定到正确的令牌。

Answer 2

在ruby2.4.2was introduced regression块解析中。在 ruby 2.4.1 中，您可以使用：

every :day { rake 'billing:daily' }

in ruby 2.4.2 如果用块调用函数参数，则必须将函数参数括在括号中，否则会得到 SyntaxError:

every(:day) { rake 'billing:daily' }

Ruby 大括号块语法在 do...end 时不起作用

Ruby curly bracket block syntax is not working while do...end works

ruby

whenever