In KnockoutJS, we can go
ko.mapping.toJS(object)
and get our object returned with observables and whatnot converted to vanilla Javascript object. Now, ko.mapping.toJS ignores computed properties. I have a scenario where I basically would like the functionality of ko.mapping.toJS to retain my pureComputed fields with whatever value they had at the time.
I've looked into the documentations page, but it looks like the "mapping options" are for the fromJS method, not toJS.
Any way I can convert my Knockout Object to a JS object but retain the pureComputeds being regular properties in the output?
I switched from ko.mapping.toJS to ko.toJS and the output of ko.toJS does include the computed properties like I want, so that seems to be all I need.
Related
I have a React component state that holds many different classes that needs to be stringify()'d. Most of the components need to be specially treated before they can be put into the JSON object. I believe that using the replacer() and if statements to check the type and then modify the output would be too cumbersome. Short of creating a custom parsing system, is there a way to customize the stringify() in what it parses?
The idea would be to have a custom function (toString() for example) in each class that when the parser reaches the class, instead of going through the key-value pairs, would call the function and append it to the JSON object.
From JSON.stringify description
If the value has a toJSON() method, it's responsible to define what data will be serialized.
Usage
JSON.stringify({ toJSON() {return {a: 'eureka'}}})
We have this data structure
[[{foo:"12", bar:"34"}, {foo:"33", bar:"55"}], [{foo:"45", bar:"67"}]]
How is it possible to make a computed property to observe a change on foo or bar?
Normally you use .#each.someProperty in a computed property to watch specific object properties in an array but in the case of nested arrays (or nested objects), you can't do .#each.#each.someProperty because .#each only works one level deep.
You need to use intermediary computed properties to raise the inner objects up one (or more) levels and have another computed property watch these in turn. There may be other ways to wire things up, but this is a pretty straightforward way to do it.
Here's a twiddle that demonstrates it. If you open the console you can see the individual computed properties recording a change occurring.
You can also use an alias to pull the inner arrays / objects up a level or two.
See twiddle here: https://ember-twiddle.com/2150099882893760cef237ff2bd22e85
Basically, in crit-service I create Ember Objects "Crits" and "Crit", and fill them with some data.
The crit-service is used by two different components, which basically do the same thing: display the Crits.
The problem is that the "change" buttons do not work. By debugging, I see that the values are changed, but the view is not updated. Why is this? Since Ember.Object is Observable, shouldn't setting a value notify the template? And most importantly, how can I get this to work?
P.S. I've seen a workaround by using Ember.A() instead of Objects. However, this would add boilerplate, as my data model is really objects and not arrays of key-value pairs.
This seems to be an issue with the {{#each-in}} helper which does not reload on changes. A quick fix is to use the {{get}} helper.
So instead of this:
{{#each-in obj as |key val|}}
{{key}}={{val}}
{{/each-in}}
Do this:
{{#each-in obj as |key|}}
{{key}}={{get obj key}}
{{/each-in}}
However, this will never work if you add additional properties.
here is a working twiddle with that solution.
Another solution that will always work is to call .rerender() on the component. This is save thanks to glimmer, which does only update the parts of the DOM that have changed. However, you would have to call it on your common root component of the two components, or on both components.
So I have this computed property inside my component.js: contexts: Ember.computed.oneWay('myService.contexts'),
And I am able to get the content from another action
openHelp(){
console.log(this.get('contexts'))
alert(this.get('contexts'))
}
}
But when I try to use the computed property in Handlebars ({{contexts}}) it's just blank.
I created an Ember Twiddle for this question: https://ember-twiddle.com/38de64d58dcf3298df6d4176f15cbc0e?openFiles=components.my-component-help.js%2Ctemplates.components.my-component-help.hbs
If I have an array foo: [ 'foo','bar'] and I do {{foo}} it outputs in handlebars. But if I make foo a computed property that gets [ 'foo','bar'] from and do {{foo}} I get nothing.
Here's the solution: https://ember-twiddle.com/e9c2ef05e27013a389e0b2bfdaec3d40?openFiles=services.my-service.js%2Ctemplates.components.my-component-help.hbs
There were two issues:
contexts is an array. When you console.log or alert it, those methods internally in some browsers JSON.stringify the object for you for your convenience. Ember will not do that. You need to format the array yourself or, as I did, each over it. For debugging purposes, feel free to use the log helper.
Computed properties on arrays are watching for array mutations through Ember's methods such as pushObject and removeObject. Simply using push or splice won't update the computed property.
Can't comment on the above answer which is correct because I don't have enough reputation, but I wanted to add a link to the documentation relating to Ember's observable methods for enumerables:
https://guides.emberjs.com/v2.5.0/object-model/enumerables/
I have a HTML fragment that iterates over key, value collection. When I create an object and put some value in, then iterate trough that object via HTML fragment, all works perfectly.
However since I need keys in specific order, I'm using a Map instead of plain object. This time when I debug I can see that my insertion order was preserved, but for some reason the HTML fragment which iterates over collection doesn't seem to know how to do so. I see nothing on my screen when I use the map object, opposed to the regular object when I see unordered content
tr ng-repeat="(key, value) in rowTitlesValues"
Is how my HTML fragment looks like, when I switch rowTitlesValues back to object works again, what am I doing wrong, and how does one keep insertion order or how do I sort object so it's keys are in custom order?
From Angular reference on ng-repeat (link):
Iterating over object properties
It is possible to get ngRepeat to iterate over the properties of an object using the following syntax:
<div ng-repeat="(key, value) in myObj"> ... </div>
You need to be aware that the JavaScript specification does not define the order of keys returned for an object. (To mitigate this in Angular 1.3 the ngRepeat directive used to sort the keys alphabetically.)
Version 1.4 removed the alphabetic sorting. We now rely on the order returned by the browser when running for key in myObj. It seems that browsers generally follow the strategy of providing keys in the order in which they were defined, [...]
If this is not desired, the recommended workaround is to convert your object into an array that is sorted into the order that you prefer before providing it to ngRepeat. You could do this with a filter such as toArrayFilter or implement a $watch on the object yourself.
Additionally, I do not think Angular 1.x knows how to iterate over a Map. I believe this line in the code proves it:
collectionKeys = [];
for (var itemKey in collection) { // iterates your object using `in`, not `of` or `Map.forEach()`
...
}
// ng-repeat then iterates the collectionKeys to create the DOM
So you will probably need to act as Angular docs suggest:
[...] convert your object into an array that is sorted into the order that you prefer before providing it to ngRepeat. You could do this with a filter such as toArrayFilter or implement a $watch on the object yourself.