ruby - 获取先前作用域的局部变量

Question

我正在制作一个要在应用程序内部使用的 Ruby REPL。我做了代码:

a = 1
b = 2
currentScope = []
Kernel.local_variables.each do |var|
    currentScope << [var,Kernel.eval(var.to_s)]
end
launchREPL(currentScope)

在 REPL 中，我可以执行以下代码:

@a     #=>1
@a+@b  #=>3

理想情况下，我不必在启动 REPL 之前编写这四行代码，而是希望在 launchREPL 函数中运行它们。然而，这需要从 launchREPL 函数内部访问之前的作用域。

---

测试1

最值得注意的是我尝试过:

launchREPL(Kernel)

当我执行以下操作时:

def launchREPL(scope)
    F = 0
    puts scope.local_variables # => [:F]
end

很明显这个方法是无效的。

测试2

launchREPL(Kernel.binding)

def launchREPL(scope)
    Kernel.binding.local_variables #= Error: private method 'local_variables' called for #<Binding>
end

有什么方法可以做我想做的事吗？

---

编辑:P.S.这是目前 launchREPL 中的代码:

def launchREPL(scope=nil,winName="Ruby REPL")
    # ICM RB file Begin:
    puts "\"Starting REPL...\""
    __b = binding   #Evaluating in a binding, keeps track of local variables
    __s = ""


    ###############################################################################
    # SEND INSTANCE VARIABLES TO REPL
    ###############################################################################
    #
    #How to prepare scope
    #   currentScope = []
    #   Kernel.local_variables.each do |var|
    #       currentScope << [var,Kernel.eval(var.to_s)]
    #   end
    #   launchREPL(currentScope)

    if scope != nil
        scope.each do |varDef|
            __b.instance_variable_set "@#{varDef[0].to_s}" , varDef[1]
            __b.eval("@#{varDef[0].to_s} = __b.instance_variable_get(:@#{varDef[0].to_s})")
        end
    end

    # to get instance variables: __b.instance_variable_get(__b.instance_variables[0])
    # or better:                 __b.instance_variable_get(:@pipe1)
    #
    ###############################################################################

    bStartup = true
    while bStartup || __s != ""
        # If startup required skip evaluation step
        if !bStartup

            #Evaluate command
            begin
                __ret = __s + "\n>" + __b.eval(__s).to_s
            rescue 
                __ret = __s + "\n> Error: " + $!.to_s
            end
            puts __ret
        else
            #REPL is already running
            bStartup = false
        end

        #Read user input & print previous output
        __s = WSApplication.input_box(__ret,winName,"")
        __s == nil ? __s = "" : nil
    end
end

Answer 1

虽然您试图实现的目标尚不清楚，而且肯定有很多方法可以正确地做到这一点，每个 ruby​​ 方法都可以用Object#send 调用方法:

def launchREPL(scope)
  scope.send :local_variables #⇒ here you go
end

a = 42
launchREPL(binding).include?(:a)
#⇒ true

---

旁注:您的“4 行”通常是这样用 ruby​​ 编写的:

local_variables.map { |var| [var, eval(var.to_s)] }

它们应该这样写(注意Binding#local_variable_get):

local_variables.map { |var| [var, binding.local_variable_get(var)] }

---

总结:

def launchREPL(scope)
  vars = scope.send(:local_variables).map do |var|
           [var, scope.local_variable_get(var)]
         end
  # some other code
end
a = 42
launchREPL(binding).to_h[:a]
#⇒ 42