Question

我想弄清楚为什么我的代码无效。如您所见，代码非常简洁。

有人可以帮我理解为什么我收到此错误消息：

“NoMethodError：undefined method`＆lt;＆lt;'为零：NilClass“

当我将此命令输入终端（加载脚本后）：

mex_cuisine.add_recipe（“charro beans”）

剧本：

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

非常感谢您的协助。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

导致相同的错误......这是长版本：

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

**编辑：

以下是给定的测试代码：

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

将以下代码放在名为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

没有错误。

Ruby newb请求基本类的帮助

1 个答案: