Question

我显然很擅长Ruby，而且编程一般，非常感谢任何帮助。

这是我的代码段：

class Player
    attr_accessor :name, :hp

    def initialize(name, hp)
        @name = name
        @hp = hp
    end

    def name
        @name
    end

    def hp
        @hp
    end
end

def prompt
    print "> "
end

prompt; pname = gets.chomp
player = Player.new(pname, rand(20..30))

puts "#{player.name} \:\: #{player.hp} HP"

def test
    puts "#{player.name} \:\: #{player.hp} HP - IN METHOD"
end

test

运行时，结果如下：

$ ruby wtf.rb

> Test Name

Test Name :: 20 HP

wtf.rb:24:in `test': undefined local variable or method `player' for main:Object (NameError) from wtf.rb:27:in `<main>'

为什么我的通话工作在第一个实例，而不是第二个？是因为它现在正在寻找一个新的＆＃34;播放器＆＃34; ＆＃34;测试＆＃34;中的变量方法？如果是这样，我如何从之前创建的类实例中调用它？

谢谢！

Answer 1

player被定义为方法test范围之外的局部变量，

将player的引用更改为@player，使其成为实例变量

以下是范围和变量的快速reference，以及similar question

作为旁注，您不应将test用作方法名称，因为它已在Kernel上定义

irb(main):001:0> method(:test)
=> #<Method: Object(Kernel)#test>

Answer 2

def test
  puts "#{player.name} \:\: #{player.hp} HP - IN METHOD"
end

您忘记将player传递给方法：

def test(player)
  puts "#{player.name} \:\: #{player.hp} HP - IN METHOD"
end

test(player) # => player = Player.new(pname, rand(20..30)) :: 22 HP - IN METHOD

Answer 3

Ruby没有像Javascript这样的函数的词法范围，所以这个（ruby）：


player = Player.new(pname, rand(20..30))
def test
    # error: undefined variable or method 'player', 
    # this happens because player was defined
    # in an unrelated scope outside this method
    puts "#{player.name} \:\: #{player.hp} HP - IN METHOD"
end
test

NOT 等效于此（javascript）


var player = new Player(pname, ...);
var test = function() {
    # works as expected, player is available because it was defined
    # in the parent scope
    console.log(player.name + "\:\:" + player.hp + " HP - IN METHOD");
};
test();

如果你想在ruby上使用类似于词法范围的东西，也许你应该使用lambda


player = Player.new(pname, rand(20..30))
test = lambda do
    # works as expected, this block scope inherits from parent scope where the block
    # was created, so, it can access player local variable
    puts "#{player.name} \:\: #{player.hp} HP - IN METHOD"
end
test.call

Ruby：从方法调用类实例时遇到麻烦

3 个答案: