Create方法中的实例变量与局部变量(Instance variable vs local variable in the Create method)

Create方法中的实例变量与局部变量(Instance variable vs local variable in the Create method)

据我所知，我们在方法new使用了一个实例变量

def new @article = Article.new end

因为这个变量也用在new.html.erb 。 （如果我错了，请纠正我）。

但是为什么我们在create方法中使用实例变量？ 在create方法之外还有哪些地方使用？ 我们不能只使用局部变量article而不是实例变量@article吗？

def create article = Article.new(article_params) if article.save flash[:success] = "Article created successfully!" redirect_to articles_url else render 'new' end end private def article_params params.require(:article).permit(:title, :body) end

As far as I understand we use namely an instance variable in the method new

def new @article = Article.new end

because this variable is used in new.html.erb too. (Please correct me if I am wrong).

But why do we use an instance variable in the create method? Where else is it used outside the create method? Can't we just use a local variable article instead of the instance variable @article?

def create article = Article.new(article_params) if article.save flash[:success] = "Article created successfully!" redirect_to articles_url else render 'new' end end private def article_params params.require(:article).permit(:title, :body) end

最满意答案

你不能，因为@article变量也用在new.html.erb文件中，当article未成功保存时呈现。

所以你会得到（据我记得的）错误undefined method 'model_name' for nil:NilClass 。

You can't, because @article variable is also used in new.html.erb file, rendered when article isn't saved successfully.

So you'll get (as far as I remember) error undefined method 'model_name' for nil:NilClass.