I've been facing a problem that is basically the following:
I have a knockout ViewModel which contains observable arrays of items with observable properties and methods.
I need to pull data from the server. The methods need to exist after data is taken from server. So I create a new ViewModel and then update its value from what comes from server. (THIS DOES NOT WORK, THE RESULTING ARRAY HAS NO ITEMS)
If I create, with mapping, a new object using var newObj = ko.mapping.fromJS(data) the resulting Array has items, but its items have no methods. It spoils my Bindings.
The fiddle of my problem: http://jsfiddle.net/claykaboom/R823a/3/ ( It works util you click in "Load Data From The Server" )
The final question is: What is the best way to have items on the final array without making the loading process too cumbersome, such as iterating through every item and filling item's properties in order to keep the previously declared methods?
Thanks,
I changed your code little bit. Check this version of JSFiddle.
var jsonFromServer = '{"ModuleId":1,"Metadatas":[{"Id":1,"MinValue":null,"MaxValue":null,"FieldName":"Teste","SelectedType":"String","SelectedOptionType":null,"IsRequired":true,"Options":[]}]}';
Your code doesnt work because your jsonFromServer variable does not contain methods we need at binding like you described in your question. ( -- > Metadatas )
So we need to define a custom create function for Metadata objects at the mapping process like this :
var mapping = {
'Metadatas': {
create: function(options) {
var newMetaData = new MetadataViewModel(options.parent);
newMetaData.Id(options.data.id);
newMetaData.FieldName(options.data.FieldName);
newMetaData.SelectedType(options.data.SelectedType);
newMetaData.SelectedOptionType(options.data.SelectedOptionType);
newMetaData.IsRequired(options.data.IsRequired);
newMetaData.Options(options.data.Options);
// You can get current viewModel instance via options.parent
// console.log(options.parent);
return newMetaData;
}
}
}
Then i changed your load function to this :
self.LoadDataFromServer = function() {
var jsonFromServer = '{"ModuleId":1,"Metadatas":[{"Id":1,"MinValue":null,"MaxValue":null,"FieldName":"Teste","SelectedType":"String","SelectedOptionType":null,"IsRequired":true,"Options":[]}]}';
ko.mapping.fromJSON(jsonFromServer, mapping, self);
}
You dont have to declare a new viewModel and call ko.applyBindings again. Assigning the updated mapping to current viewModel is enough. For more information check this link. Look out for customizing object construction part.
The final question is: What is the best way to have items on the final
array without making the loading process too cumbersome, such as
iterating through every item and filling item's properties in order to
keep the previously declared methods?
As far as i know there is no easy way to do this with your object implemantation. Your objects are not simple. They contains both data and functions together. So you need to define custom create function for them. But if you can able to separate this like below then you dont have to customize object construction.
For example seperate the MetadataViewModel to two different object :
--> Metadata : which contains only simple data
--> MetadataViewModel : which contains Metadata observableArray and its Metadata manipulator functions
With this structure you can call ko.mapping.fromJSON(newMetaDataArray , {} , MetadataViewModelInstance.MetadataArray) without defining a custom create function at the mapping process.
Related
I would like to extend an existing datamodel in Microstream with a new data object. E.g. I have Customers, with data records in Microstream, and I would like to add Vendors, with their own datastructure and data. As the database is not empty, I cannot start as if their is no data, however adding a list of Vendor to the dataroot doesn't seem to work. Microstream says the list is null when starting, which is correct, but I cannot add my new object to a null list. Can someone explain me how to add a vendor to my 'database' ?
You just need to add this List and store this object with the existing list again.
I received an answer from fh-ms # Microstream:
Hi, you are right, the vendors list is not present in the storage, so the field will be initialized with its default value (null).
There are several possibilities to introduce initial values to new fields.
One rather complex way would be to implement a Legacy Type Handler.
A far more simple one is just lazy initialization in your Customer type:
public List<Vendor> getVendors()
{
if(this.vendors == null)
{
this.vendors = new ArrayList<>()
}
return this.vendors;
}
And that works !
Right now, if I add a field to a Parse object and then save it, the new column shows up in the Parse dashboard.
For example, after running:
let media = new Parse.Object("Media");
media.set("foo", "bar");
await media.save();
I will have a new column called foo.
Is it possible to prevent this from happening?
Yes. This can be done using class-level permissions, which allow you to prevent fields being added to classes.
Parse lets you specify what operations are allowed per class. This lets you restrict the ways in which clients can access or modify your classes.
...
Add fields: Parse classes have schemas that are inferred when objects are created. While you’re developing your app, this is great, because you can add a new field to your object without having to make any changes on the backend. But once you ship your app, it’s very rare to need to add new fields to your classes automatically. You should pretty much always turn off this permission for all of your classes when you submit your app to the public.
You would have to add a beforeSave trigger for every one of your classes, keep a schema of all your keys, iterate over the request.object's keys, and see if there are any that do not belong in your schema. You can then either un-set them and call response.success(), or you can call response.error() to block the save entirely, preferably with a message indicating the offending field(s).
const approvedFields = ["field1", "field2", "field3"];
Parse.Cloud.beforeSave("MyClass", function(request, response) {
let object = request.object;
for( var key in object.dirtyKeys() ) {
if( approviedFields.indexOf(key) == -1 ) return response.error(`Error: Attempt to save invalid field: ${key});
}
response.success();
});
Edit:
Since this got a little attention, I thought I'd add that you can get the current schema of your class. From the docs: https://docs.parseplatform.org/js/guide/#schema
// create an instance to manage your class
const mySchema = new Parse.Schema('MyClass');
// gets the current schema data
mySchema.get();
It's not clear if that's async or not (you'll have to test yourself, feel free to comment update the answer once you know!)
However, once you have the schema, it has a fields property, which is an object. Check the link for what those look like.
You could validate an object by iterating over it's keys, and seeing if the schema.fields has that property:
Parse.Cloud.beforeSave('MyClass', (request, response) => {
let object = request.object;
for( var key in object.dirtyKeys() ) {
if( !schema.fields.hasOwnProperty(key) ) < Unset or return error >
}
response.success();
}
And an obligatory note for anyone just starting with Parse-Server on the latest version ,the request scheme has changed to no longer use a response object. You just return the result. So, keep that in mind.
Beginner question : I've worked through the Try Meteor tutorial. I've got fields in my HTML doc, backed by helper functions that reference collections, and BOOM --> the fields are updated when the data changes in the DB.
With the "Hide completed" checkbox, I've also seen data-binding to a session variable. The state of the checkbox is stored in the Session object by an event handler and BOOM --> the list view is updated "automatically" by its helper when this value changes. It seems a little odd to be assigning to a session object in a single page application.
Through all this, my js assigns nothing in global scope, I've created no objects, and I've mostly seen just pipeline code, getting values from one spot to another. The little conditional logic is sprayed about wherever it is needed.
THE QUESTION... Now I want to construct a model of my business data in javascript, modelling my business rules, and then bind html fields to this model. For example, I want to model a user, giving it an isVeryBusy property, and a rule that sets isVeryBusy=true if noTasks > 5. I want the property and the rule to be isolated in a "pure" business object, away from helpers, events, and the meteor user object. I want these business objects available everywhere, so I could make a restriction, say, to not assign tasks to users who are very busy, enforced on the server. I might also want a display rule to only display the first 100 chars of other peoples tasks if a user isVeryBusy. Where is the right place to create this user object, and how do I bind to it from my HTML?
You can (and probably should) use any package which allows you to attach a Schema to your models.
Have a look at:
https://github.com/aldeed/meteor-collection2
https://github.com/aldeed/meteor-simple-schema
By using a schema you can define fields, which are calculated based on other fields, see the autoValue property: https://github.com/aldeed/meteor-collection2#autovalue
Then you can do something like this:
// Schema definition of User
{
...,
isVeryBusy: {
type: Boolean,
autoValue: function() {
return this.tasks.length > 5;
}
},
...
}
For all your basic questions, I can strongly recommend to read the DiscoverMeteor Book (https://www.discovermeteor.com/). You can read it in like 1-2 days and it will explain all those basic questions in a really comprehensible way.
Best Regards,
There is a very good package to implement the solution you are looking for. It is created by David Burles and it's called "meteor-collection-helper". Here it the atmosphere link:
You should check the link to see the examples presented there but according to the description you could implement some of the functionality you mentioned like this:
// Define the collections
Clients = new Mongo.Collection('clients');
Tasks = new Mongo.Collection('tasks');
// Define the Clients collection helpers
Clients.helpers({
isVeryBusy: function(){
return this.tasks.length > 5;
}
});
// Now we can call it either on the client or on the server
if (Meteor.isClient){
var client = Clients.findOne({_id: 123});
if ( client.isVeryBusy() ) runSomeCode();
}
// Of course you can use them inside a Meteor Method.
Meteor.methods({
addTaskToClient: function(id, task){
var client = Clients.findOne({_id: id});
if (!client.isVeryBusy()){
task._client = id;
Tasks.insert(task, function(err, _id){
Clients.update({_id: client._id}, { $addToSet: { tasks: _id } });
});
}
}
});
// You can also refer to other collections inside the helpers
Tasks.helpers({
client: function(){
return Clients.findOne({_id: this._client});
}
});
You can see that inside the helper the context is the document transformed with all the methods you provided. Since Collections are ussually available to both the client and the server, you can access this functionality everywhere.
I hope this helps.
I have a property called Copies which is defined on the server that represents the default number of copies allowed. And I can update this value and it will update an input field on my UI.
however, I would like to be able to reset the Copies property to the original value if the user resets this field on the UI.
My idea was to define a custom property on my kendo datasource model called originalValue that references the Copies property. but this just seems to override the Copies property if I do something like this.
schema: {
data: 'd',
total: function (data) {
return data.d.length;
},
model: {
originalCopies: "Copies"
}
}
how can I go about creating a custom property like this which is basically a immutable clone of my Copies property?
You can try to do it on the server side, just create a separate property "OriginalCopies" and set it to Copies. Once passed to the client side , it will lose its immutability.
Something similar could be done on the client side as well. JSON.stringify your Copies and set
OriginalCopies to the JSON.parse value of the stringified variable as:
var copies = JSON.stringify(data.Copies);
data.OriginalCopies = JSON.parse(copies);
I am using Datamapper ORM 1.8.2.1 with CodeIgniter 2.1.0 and I have trouble accessing newly added related objects from within a parent.
I have a parent class like this:
class Virement extends DataMapper
{
var $has_many = array("lignevirement");
// ...
}
and a child class like this:
class LigneVirement extends DataMapper
{
var $has_one = array("virement");
// ...
}
In the user code, I instantiate this parent and add a few child objects:
$vrt = new Virement; // and do some inits on properties.
$vrt->save();
$lili = new LigneVirement; // do some inits also on properties.
$lili->save();
$vrt->save($lili);
$lili = new LigneVirement; // do some inits also on properties.
$lili->save();
$vrt->save($lili);
// ...
When I then count immediately after the added child objects, I get 0 :
echo $vrt->lignevirement->count();
... whereas taking a look in the database table shows that the parent record has been added, all the child records have been added, and they are correctly related with the parent record.
By the way, when I then try this workaround, I get the correct number of child rows:
$vrt = new Virement($vrt->id);
So what might be wrong with my code above ?
In my experience, Datamapper doesn't make related objects accessible immediately after a save. This includes displaying the properties of a related object; to follow on from your example, the following code will not display the ID of the $vrt object:
$vrt = new Virement;
$vrt->get_by_id(1);
$li = new LigneVirement;
$li->save($vrt);
echo $li->vrt->id;
However, if you redirect, or reload the page, and then reload the $li object, all related items will be available as expected.
If you really need to have related items immediately available, you can create a new related object and load it based on the _id value, as you suggest. Something like:
$vrt = new Virement;
$vrt->get_by_id(1);
$li = new LigneVirement;
$li->save($vrt);
$vrt_refresh = new Virement;
$vrt_refresh->get_by_id($li->vrt_id);
echo $vrt_refresh->id;
(Obviously the above code would be unnecessary, as you already know the ID of the $vrt object, but this is the general principle).
Incidentally, regarding the note in your comment about Datamapper using the same ID for two new objects, I'd avoid using the same variable name for both the objects; this will be unreliable in my experience. Instead, use different variable names, or (if this is unavoidable) take a look at the "Clear" method: http://datamapper.wanwizard.eu/pages/utility.html#clear .