I was reading a book and in a chapter about Controllers when it talks about rendering stuff, for JSON it has an example like this but doesn't go in to details so I couldn't figure out the bigger picture that this example fits in:
render :json => @projects, :include => tasks
And also some example with JSONP using it with callback functions:
render :json => @record, :callback => 'updateRecordDisplay'
Can someone explain these?
您通常会返回JSON，因为:
A) 您正在将应用程序的部分/全部构建为单页应用程序(SPA)，并且需要客户端JavaScript能够在不完全重新加载页面的情况下拉入额外数据.
or个
B) You are building an API that third parties will be consuming and you have decided to use JSON to serialize your data.
或者，你可能正在吃自己的狗粮，做both次
In both cases render :json => some_data will JSON-ify the provided data. The :callback key in the second example needs a bit more explaining (see below), but it is another variation on the same idea (returning data in a way that JavaScript can easily handle.)
:callback?JSONP(第二个示例)是绕过Same Origin Policy的一种方式，它是每个浏览器内置安全性的一部分.如果您的API是api.yoursite.com，并且您将为services.yoursite.com以上的应用程序提供服务，那么您的JavaScript(缺省情况下)将不能发出从services到api的XMLHttpRequest(XHR-又名AJAX)请求.人们一直在偷偷绕过这一限制的方式(在Cross-Origin Resource Sharing spec was finalized之前)是通过从服务器as if it was JavaScript instead of JSON发送JSON数据).因此，与其送回:
{"name": "John", "age": 45}
the server instead would send back:
valueOfCallbackHere({"name": "John", "age": 45})
因此，客户端JS应用程序可以创建指向api.yoursite.com/your/endpoint?name=John的script标记，并具有名为with the data from this other origin的valueOfCallbackHere函数(必须在客户端JS中定义)