Came across this strange result today trying to render a list of objects as JSON in Grails 2.0.4...(i know i'm gonna regret asking this on account of something right under my nose...updated 5/26, my prediction was correct, see below :-))
This works fine; the JSON renders correctly in the browser...
def products = [] //ArrayList of Product objects from service
def model = (products) ? [products:products] : [products:"No products found"]
render model as JSON
..so why doesn't this shortened version without model
work?
def products = []
render ((products) ? [products:products] : [products:"No products found"]) as JSON
The resulting JSON from the above code is output as a single line of text, so I suspect it's not picking up as JSON
, but it's parenthesized correctly, so what's the deal?
['products':[com.test.domain.Product : null, com.test.domain.Product...]
Conditional Rendering. In React, you can create distinct components that encapsulate behavior you need. Then, you can render only some of them, depending on the state of your application. Conditional rendering in React works the same way conditions work in JavaScript.
Conditional Rendering 1 Element Variables. You can use variables to store elements. ... 2 Inline If with Logical && Operator. You may embed expressions in JSX by wrapping them in curly braces. ... 3 Inline If-Else with Conditional Operator. ... 4 Preventing Component from Rendering. ...
Another method for conditionally rendering elements inline is to use the JavaScript conditional operator condition ? true : false. In the example below, we use it to conditionally render a small block of text. It can also be used for larger expressions although it is less obvious what’s going on:
To render different forms of responses from simple text responses, to view and templates. A multi-purpose method for rendering responses to the client which is best illustrated with a few examples! Warning - this method does not always support multiple parameters.
This is a normal behavior of render
. When you provide arguments to render
without braces like
render model as JSON
It makes an implicit adjustment setting up the content-type
to text/json
. But in the later case, you have unknowingly made the render
to use the braces like [mark on the first brace after render
makes render use the normal render()
]
render ((products) ? [products:products] : [products:"No products found"]) as JSON
.
In the above case, you have to pass in the named parameters to render
mentioning the contentType
, text
or model
, status
etc. So in order to render the inline control logic as JSON in browser/view you have to do like below:
render(contentType: "application/json", text: [products: (products ?: "No products found")] as JSON)
You can also use content-type
as text/json
. I prefer application/json
.
UPDATE
Alternative Simplest Way:render([products: (products ?: "No products found")] as JSON)
The essence of your problem here is that the groovy compiler interprets
render x as JSON
to mean
render (x as JSON)
but it interprets
render (x) as JSON
to mean
(render x) as JSON
If a method name (in this case render
) is followed immediately by an opening parenthesis, then only code up to the matching closing parenthesis is considered to be the argument list. This is why you need an extra set of parentheses to say
render ((x) as JSON)
Don't know the reason. Try to use like this:
render(contentType: 'text/json') {[
'products': products ? : "No products found"
]}
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