Fancytree complains Ajax request returned a string using Cherrypy - ajax

Question

Hi I am very new to use cherrypy as backend with fanytree as front end.
here is my fanytree side of the code:
source: {
url : '/test_data'
},
on the cherrypy side, I implemented function called test_data
#cherrypy.expose
#cherrypy.tools.json_out()
def test_data(self, **kwargs):
cherrypy.response.headers["Content-Type"] = "application/json"
return '[ {"title":"abc", "folder": true, "key": "1", "children":[ {"title":"b","key":"2"}] }]'
So I see the request comes to cherrypy as
'GET /test_data?_=some number...
On browser I see my return object back but it failed on check:
if (typeof data === "string") {
$.error("Ajax request returned a string (did you get the JSON dataType wrong?).");
}
I read somewhere that you need content-type to be json but I already have. What am I missing?

Answer 1

CherryPy JSON output tool, cherrypy.tools.json_out, takes care of MIME and turning your data into a JSON string. So if you use it the method should look like:
#cherrypy.expose
#cherrypy.tools.json_out()
def test_data(self, **kwargs):
return [{
"title" : "abc",
"folder" : True,
"key" : 1,
"children" : [{"title": "b", "key": 2}]
}]
Otherwise if you want to do it yourself it'll be:
import json
#cherrypy.expose
def test_data(self, **kwargs):
cherrypy.response.headers["Content-Type"] = "application/json"
return json.dumps([{
"title" : "abc",
"folder" : True,
"key" : 1,
"children" : [{"title": "b", "key": 2}]
}])
Then make sure you've restarted CherryPy app, and look in web developer tools or FireBug network tab to verify response headers and content.

Answer 2

The content type is ok, but the string you are returning is not valid json (for example the keys must be enclosed in double quotes).
I would recommend to prepare your data as list of dicts and then use 'json.dumps()' to convert to JSON.
(Maybe the json_out tool does the same but I would guess that even then you should return a list of dicts instead of a string.)