Ruby newb 请求基本类的帮助

Question

我想弄清楚为什么下面的代码不起作用。如您所见，代码非常简洁。

有人可以帮我理解为什么我会收到此错误消息：

"NoMethodError: 未定义的方法 `

当我将此命令输入终端时（加载脚本后）：

mex_cuisine.add_recipe("charro beans")

脚本：

class Cookbook

    attr_accessor :title, :recipes, :recipe
    def initialize(title)
        @title = title
        @recipes = []
    end

    def add_recipe(recipe)
        @recipe = recipe
        @recipes << @recipe
    end
end

class Recipe

    attr_accessor :name, :ingredients, :steps
    def initialize(name, ingredients, steps)
        @name = name
        @ingredients = ingredients
        @steps = steps
    end

end

非常感谢您的帮助。 谢谢。

**编辑：

替换此代码：

def add_recipe(recipe)
    @recipes.push(recipe)
    puts "Added a recipe to the collection: #{recipe.title}"
end

导致同样的错误...这是长版本：

NoMethodError: 未定义的方法push' for nil:NilClass from cookbook.rb:10:inadd_recipe' 来自 (irb):173 来自 /Users/patrickmeaney/.rvm/rubies/ruby-2.1.1/bin/irb:11:in `'

**编辑：

这是给定的测试代码：

mex_cuisine = Cookbook.new("Mexican Cooking")
burrito = Recipe.new("Bean Burrito", ["tortilla", "bean"], ["heat beans", "place beans in tortilla", "roll up"])

mex_cuisine.recipes # []
mex_cuisine.add_recipe(burrito)

Answer 1

将以下代码放入名为 my_prog.rb 的文件中：

class Cookbook

    attr_accessor :title, :recipes, :recipe
    def initialize(title)
        @title = title
        @recipes = []
    end

    def add_recipe(recipe)
        @recipe = recipe
        @recipes << @recipe
    end
end

class Recipe

    attr_accessor :name, :ingredients, :steps
    def initialize(name, ingredients, steps)
        @name = name
        @ingredients = ingredients
        @steps = steps
    end

end

class Cookbook

    attr_accessor :title, :recipes, :recipe
    def initialize(title)
        @title = title
        @recipes = []
    end

    def add_recipe(recipe)
        @recipe = recipe
        @recipes << @recipe
    end
end

class Recipe

    attr_accessor :name, :ingredients, :steps
    def initialize(name, ingredients, steps)
        @name = name
        @ingredients = ingredients
        @steps = steps
    end

end

mex_cuisine = Cookbook.new("Mexican Cooking")
burrito = Recipe.new("Bean Burrito", ["tortilla", "bean"], ["heat beans", "place beans in tortilla", "roll up"])

mex_cuisine.recipes # []
mex_cuisine.add_recipe(burrito)

打开一个终端窗口并 cd 到与 my_prog.rb 相同的目录。然后运行你的程序：

ruby my_prog.rb

不会有错误。