如何在rails3中自定义to_json方法？ [英] How to customize the to_json method in rails3?

问题描述

我想将一个Place对象数组转换为json，我一直这样做：

I want to convert an array of Place objects to json, I've been doing it like this:

var places = <%= @places.to_json.html_safe %>;

唯一的问题是@places数组中的每个位置都有一个不相关的标记列表包括在内。我正在使用acts_as_taggable_on gem来处理标签，所以要获取一个地方的标签列表，我需要说place.tag_list。

The only problem is that every place in the @places array has an associated tag list that doesn't get included. I'm using the acts_as_taggable_on gem to handle tags, so to get the tag list for a place I need to say place.tag_list.

我该怎么办？获取javascript数组中每个位置的tag_list？我想我需要编写自己的to_json方法，但我不知道如何。

What do I have to do to get the tag_list included for each place in the javascript array? I think I'll need to write my own to_json method but I don't know how.

编辑

事实证明，这比我意识到的要容易。我能够这样说：

It turns out that this is easier than I realized. I was able to say this:

var places = <%= @places.to_json(:include => :tags).html_safe %>

唯一的问题是，这包含有关每个标签的更多信息，而不是我真正需要的。每个标签都有一个id和名称，我真正想要的只是一个带有标签名称的列表。

The only problem is that this includes more information about each tag than I really need. Every tag has an id and name, what I really want is just a list with tag names in it.

推荐答案

to_json 方法也接受一个名为<$ c $的参数C>方法。此参数允许您指定应调用并包含在对象的json表示中的方法。既然你提到你有一个名为 tag_list 的方法，你可以这样做：

The to_json method also accepts an argument called methods. This argument allows you to specify methods that should be called and included in the json representation of the object. Since you mentioned that you have a method called tag_list, you can do this:

var places = <%= @places.to_json(:methods => :tag_list).html_safe %>

如果出于某种原因，您没有生成标签名称的方法，但每个标签有一个方法可以给你它的名字，你可以在你的 Place 模型中添加一个方法来生成一个标签名称列表，如下所示：

If, for some reason, you don't have a method to produce tag names, but each tag has a method to give you its name, you could add a method inside your Place model to produce a list of tag names like so:

def tag_names
    tags.collect do |tag|
        tag.name
    end
end

然后你就可以得到你的地方json与 tag_names 这样：

Then you could get your places json with tag_names like this:

place_json = @places.to_json(:methods => :tag_names)

此技术适用于您所有的计算属性喜欢添加到模型的json表示。

This technique will work for any computed attributes you'd like to add to a model's json representation.

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