How do you access a mapped sourceParent? #15

Closed
crockpotveggies opened this Issue Apr 5, 2012 · 5 comments

Comments

Projects
None yet
2 participants
@crockpotveggies

Thought I had found all of the caveats, but maybe this is a limitation of mapping ;)

In your seating chart example you have arg.targetParent.id. However, what if that ID of the target parent was mapped using the mapping plugin?

I tried multiple methods to access it but the common error was cannot access __ko_mapping__ of undefined. http://jsfiddle.net/DeLongey/F782z/

Do I write my own handlers for this?

@rniemeyer

This comment has been minimized.

Show comment Hide comment
@rniemeyer

rniemeyer Apr 5, 2012

Owner

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.

Owner

rniemeyer commented Apr 5, 2012

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

This comment has been minimized.

Show comment Hide comment
@crockpotveggies

crockpotveggies Apr 5, 2012

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.

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

This comment has been minimized.

Show comment Hide comment
@rniemeyer

rniemeyer Apr 5, 2012

Owner

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.

Owner

rniemeyer commented Apr 5, 2012

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

This comment has been minimized.

Show comment Hide comment
@crockpotveggies

crockpotveggies Apr 5, 2012

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!

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

This comment has been minimized.

Show comment Hide comment
@rniemeyer

rniemeyer Apr 6, 2012

Owner

OK- glad that you got it working!

Owner

rniemeyer commented Apr 6, 2012

OK- glad that you got it working!

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment