ruby - 如何在 Ruby 中为 String 类创建新函数？

Question

我想检查我遇到的字符串类型:

class String
    def is_i?
        /\A[-+]?\d+\z/ === self
    end

    def is_path?
        pn = Pathname.new(self)
        pn.directory?
    end     
end

def check(key)
    puts case key
    when is_i?
        puts "Could be a number"
    when is_path?
        puts "This is a path"
    else
        puts "Ok"
    end
end

当我运行 check("1345425") 时，出现以下错误:

undefined method `is_i?' for main:Object (NoMethodError)

我应该做什么来纠正它？

Answer 1

您已在 String 实例上定义了函数，因此:

def check(key)
    puts case
         when key.is_i?
           "Could be a number"
         when key.is_path?
           "This is a path"
         else
           "Ok"
         end
end

或

def check(key)
    puts case key
         when ->(s) { s.is_i? }
           "Could be a number"
         when ->(s) { s.is_path? }
           "This is a path"
         else
           "Ok"
         end
end

UPD 另请注意，我删除了对 puts 的多余后续调用。