How do you access a mapped sourceParent?

[rniemeyer]

How do you access a mapped sourceParent?

[rniemeyer]

You are given the observableArray as the targetParent. It is up to you to decide how you will identify it. The mapping plugin will put your items into it with their properties, but it won't add properties directly on the observableArray itself.

So, you could choose to add the id property to your observableArrays yourself or in the "create" callback of the mapping plugin.

Alternatively, you could do some comparison yourself like arg.targetParent === self.engineModel.users

Would be happy to help you further with this one.

[crockpotveggies]

I think you qualify as Knockout's best evangelist ;)

I tried to do some research before blindly asking for help, but this was as far as I got from this SO question: http://stackoverflow.com/questions/8401799/knockoutjs-adding-observable-properties-and-functions-to-objects-in-a-mapping-g

var mapping = {
        "users": {
            key: function(data) { return ko.utils.unwrapObservable(data.id); },
            create: function(options) {
                return createUser(options.data);
            }
        },
        "jobs": {
            key: function(data) { return ko.utils.unwrapObservable(data.id); }
        }
    };
    var createUser = function(user) {
        var result = ko.mapping.fromJS(user);
        result.parentId = user.id;
        return result;
    };

My usual attempts to then access arg.targetParent.parentId either yielded undefined or has no method 'parentId'. Your guidance is much appreciated :)

If you feel this needs to move to StackOverflow out of GitHub Issues I can open up a question.

[rniemeyer]

In this case, the parentId is being added to the item rather than the observableArray itself. You would be able to read it off arg.item though. Not sure if that is what you want to do?

Otherwise, you could do:

var createUser = function(user) {
    var result = ko.mapping.fromJS(user);
    result.jobs.userId = user.id;
    return result;
};

Like: http://jsfiddle.net/rniemeyer/F782z/8/

No problem keeping this issue here. We can keep working on it, until we get it solved for you.

[crockpotveggies]

Your method was much more brilliant than my hack.

I created a temporary solution but I was not impressed with its performance: http://jsfiddle.net/DeLongey/ZnhtB/ essentially I parsed the DOM to grab the ID, but that defeats the whole purpose LOL

So to settle this issue and help my understanding (and future readers), in order to access a property I want in the observableArray from a parent, I need to set the child's properties by chaining them when creating the parent (like as in your response).

I was unaware that it would work (I was afraid it would interfere with the child). I can confirm it indeed works :) and in fact this simplifies my coding even further.

Thank you very much! Learned a lot!

[rniemeyer]

OK- glad that you got it working!