i've been trying to trigger Vue DOM updates by updating an array the old way and it obviously wont do it because of the ceveats on Vue detecting object/array changes. I dont know how to access my nested array properties by using Vue.set. Normally i would access and assign my property like this (by the way this is a state in Vuex):
state.timelines[0].events[0].item.info = payload.info
I dont know how to access and assign that property with .set, i've tried a few combinations but they failed to work. Thanks.
Solution: when trying to alter an object property, even if its deep in nested arrays, just use: Vue.set(arrayA[indexA].arrayB[indexB].object('objectPropertyName', newValue))
If dealing with arrays use:
Vue.set(array, arrayIndex, newValue).
Related
I've finally started to understand a lot of info regarding FireStore, but I'm wondering if I can get some assistance.
If I had a setup similar to or like this:
races
Android
name: Android
size: medium
stats <---- this is the map
str: 10
sex: 12.... (more values)
How would I parse this? I am looking to make specific TextViews apply values found in the database so that I can simply update the database and my app will populate those values so that hard coding and code updating won't be nearly as troublesome in the future.
I currently use something like this:
val androidRef = db.collection("races").document("Android")
androidRef.get().addOnSuccessListener { document ->
if (document != null) {
oneOfTheTextViews.text = document.getString("str")
} else {
}
The issue is currently I can only seem to access from collection (races) / document (android) / then a single field (I have "str" set as a single field, not part of a map or array)
What would the best practice be to do this? Should I not nest them at all? And if I can reference said nesting/mapping/array, what functions need to be called? (To be clear, I am not asking only whether or not it is possible - the reference guides and documents allude to such - but what property/class/method/etc needs to be called in order to access only one of those values or point to one of those values?).
Second question: Is there a way to get a list of document names? If I have several races, and simply want to make a spinner or recycler view based on document names as part of a collection, can I read that to the app?
What would the best practice be to do this?
If you want to get the value of your str property which is nested within your stats map, please change the following line of code:
oneOfTheTextViews.text = document.getString("str")
to
oneOfTheTextViews.text = document.getString("stats.str")
If your str property is a number and not a String, then instead of the above line of code please use this one:
oneOfTheTextViews.text = document.getLong("stats.str")
Should I not nest them at all?
No, you can nest as many properties as you want within a Map.
Is there a way to get a list of document names?
Yes, simply iterate the collection and get the document ids using getId() function.
I generally have problems using rxjs with nested Objects or Arrays.
My current use-case is this:
{a: [
{b: 0, c:[{d:1}]},
{b: 1, e:[{f: 'someString'}]}
]
Task: Get and set the Observable or value of a,b,c,d,e,f. I also want to be able to subscribe to each property.
I had this Problem in a similar use-case with an Array of BehaviorSubjects:
Efficiently get Observable of an array BehaviorSubjects
I generally have problems to use the basic functionality of nested arrays/objects in rxjs.
The basic functionality I mean includes:
Array:
getting Element by Index
using for of/in on Arrays
setting an Element by Index
push, pop, shift, slice, splice, ...
Object:
getting Value by Property name
going into the nested tree: object.key1.key2.key3[3].key4 ...
setting Value by Property name
assign
for of/in loops
Generally:
Destructuring: e.g.: let [variable1, variable2] = someObject;
Maybe other stuff I forgot.
I dont know if and which functions are possible for which rxjs Objects and which make sense (for example you should be able to set values in an Observable directly). But coming from a background without rxjs, I have trouble to manage my rxjs Objects properly.
I think reason for this besides my lack of knowledge and understanding is, that
a. The rxjs Objects don't provide the functionality as I'm used to from normal arrays and objects. e.g.:
let variable1 = array[1].property;
//becomes this (see related stack-Question I mentioned earlier)
let variable2 = array.pipe(mergeMap(d=> d[index].pipe(map(d1 => d1[property]));
// -> what happens here? You first need to know what mergeMap,
// map is doing and you have 5 levels of nested inline functions.
b. To implement the those mentioned functionalities I need to go over the .pipe() function and use some function like mergeMap, map, pluck, ... Functions that aren't directly indicating that you can get the Observable of let's say 'e' in my example. Making something like object.a[1].e wierd to implement (at least I don't know how to do that yet)
EDIT:
I also want to note, that I still love the idea of rxjs which works well in angular. I just have problems using it to it's full extend, as I'm a bit new to angular and consequently rxjs.
I thin RX is mainly focus on dealing with async operations. Mutation of array and object we can perfectly use the methods comes natively with javascript if theres no existing operators. or you can create your own operator for mutation/iteration etc.
Will try to answer some of your question on array/objects mutation, they are actually very straight forward.
Array:
getting Element by Index
map(arr=>arr[index])
using for of/in on Arrays
map(arr=>arry.map(item=>....))
setting an Element by Index
tap(arr=>arr[index]=somevalue)
Object:
getting Value by Property name
pluck('name')
going into the nested tree: object.key1.key2.key3[3].key4 ...
pluck('key1','key2')
setting Value by Property name
map(obj=>({a:value,obj...}))
assign
lets say your really want some pick array index method as rxjs operator you can create something like, same as for..in operations.
const pluckIndex=(index)=>source=>source.pipe(map(arr=>arr[index]))
const source = of([2,3])
source.pipe(pluckIndex(1)).subscribe(x => console.log(x));
It seems that angular.copy() is not properly working on one of the items that I am using it on. Here's the sample code and the screenshot that follows.
console.log("Copy");
$scope.traffic_data = traffic_data;
$scope.total_data = total_data;
console.log($scope.traffic_data);
console.log($scope.total_data);
console.log("Original");
$rootScope.original_traffic_data = angular.copy($scope.traffic_data);
$rootScope.original_total_data = angular.copy($scope.total_data);
console.log($rootScope.original_traffic_data);
console.log($rootScope.original_total_data);
console.log("Variable data");
console.log(total_data);
console.log("=============");
The problem I am facing is that the
$rootscope.original_total_data
is not copying the contents of the
$scope.total_data
as seen on the screenshot. I have highlighted the different console logs to differentiate them from one another.
The line
console.log($rootScope.original_total_data);
shows no contents even though I have used angular.copy on that variable.
What am I missing here? Please help. Thanks.
Also $rootScope is already declared in the controller and it is working for the
$rootScope.original_traffic_data
so why is it not working for
$rootScope.original_total_data?
Thanks.
total_data is an array, whereas traffic_data is an object.
angular.copy() distinguishes between arrays and objects. For objects it will copy all the keys (properties). For arrays, it will only copy the array elements and not any custom properties attached to it - see source code.
If you want to set properties on total_data, you should make it into an object instead. It does not appear to have any indexed values, so this should not be a problem, and it probably should have been an object in the first place.
I need to implement change tracking for state of any object.
How would I implement it?
For example:
let complexObject = {
/// ... mant many arrays and propertiess
}
let hash = convertToHash(complexObject)
let trackingArray = []
trackingArray.push(hash);
/// what from here and how to imlement it?
I would recommend you to use https://facebook.github.io/immutable-js/ when you change something you will get a new object. It will be much more efficient than creating a hash because you will not need to iterate the entire object graph.
Also it shares some memory internally so it will be more efficient than storing full clones in memory.
Assuming you are implementing change tracking for purpose of undo/redo functionality.
One way is to use immutable objects and store on stack old object each time when there is action invoked.
In order to capture change to objects you could use https://en.wikipedia.org/wiki/Command_pattern or redux (widely popular in react, implementation for angular).
I have a collection(arraylist) of Ref `s ,the objectify documentation says that I need to initialize collections for them to be persisted and hence modified in the future.....
Now , Ref points to an object but when I launch my app for the first time I dont have any objects in the data store...so whats the best way for me to initialize a dummy value......
Is my assumption that a Ref<> needs to point to a real object in the data store?
Two things:
You should just initialize an empty collection. You don't need to add anything to it. eg, field = new ArrayList<Ref<Thing>>();
It's actually not even required that you initialize the collection. It's just a good idea for reasons that will become apparent if you use the system for a while.