How can I update an existing JSON object's parameters in Grails? - json

Question

I'm making a todo list. When first entering the item and adding it to the list, the server works great. It takes the parameters that the user selects and passes them into a list on the server that can be viewed by rendering Item.list(), that looks like so:
[{"class":"server.Item","id":1,"assignedTo":"User 1","comments":null,"completed":false,"creator":"User 1","name":"Task 1","priority":"1","type":"Personal"},
{"class":"server.Item","id":2,"assignedTo":"User 2","comments":null,"completed":false,"creator":"User 2","name":"Er","priority":"3","type":"Work"},
{"class":"server.Item","id":3,"assignedTo":"User 1","comments":null,"completed":false,"creator":"User 2","name":"Ga","priority":"1","type":"Work"}]
Now, the user then has the option to edit the task later. On the client side this works fine, but then I need the user to be able to save the new, updated task.
This is my current update function:
def updateList() {
def newItem = Item.findById(request.JSON.id)
newItem.assignedTo = request.JSON.assignedTo
newItem.comments = request.JSON.comments
newItem.completed = request.JSON.completed
newItem.creator = request.JSON.creator
newItem.name = request.JSON.name
newItem.priority = request.JSON.priority
newItem.type = request.JSON.type
newItem.save(flush: true)
render newItem as JSON
}
This doesn't work, however. I get a null pointer exception that says "Cannot set property "assignedTo" on null object. I'm assuming that the findById request is not getting anything for the JSON object, and thus there is no object to assign values to, however I don't know what the problem is considering the items are in fact being put into the Item.list().
This is called with the following JS function on the client side:
$scope.updateList = function() {
angular.forEach($scope.items, function (item) {
// serverList.save({command: 'updateList'}, item);
$http.post('http://localhost:8080/server/todoList/updateList', item)
.success(function(response) {})
.error(function(response) {alert("Failed to update");});
});
};

Answer 1

This might depend on your Grails version, but you should be able to do this:
def update(Item item) {
if (!item) {
// return a 404
} else {
// you should really use a service and not save
// in the controller
itemService.update(item)
respond item
}
}
Grails is smart enough look that item up since there is an ID in the JSON params, and populate the object correctly.

Answer 2

Sort of a work around for anyone else that may need to do this in a basic manner, what I've done that works is clear the list when "Update List" is clicked, then read back in the values that are currently in the client side list.
Grails:
def clearList() {
Item.executeUpdate('delete from Item')
render Item.list()
}
def updateList() {
def newItem = new Item(request.JSON)
newItem.save(flush:true)
render newItem as JSON
}
Javascript:
$scope.updateList = function() { // Update list on the server
serverList.get({command: 'clearList'});
angular.forEach($scope.items, function (item) {
serverList.save({command: 'updateList'}, item);
});
};