Develop Reference

Delete Nested Reference in Firestore

I am trying to delete a 2 levels deep nested Reference in Firestore. My Schema looks like this:
In Code it looks like this:
{
"folder": "bla",
"title": "myTitle",
"children": [
{
"ref": "firstReference"
},
{
"ref": "secondReference"
},
{
"title": "Subcollection Title",
"children": [
{
"ref": "thirdReference"
},
{
"ref": "forthReference"
}
]
}
]
}
Now i am searching a way to remove the third or forth Reference from the second children array.
To remove an item from the first children array is use this code:
docRef.update({children: firebase.firestore.FieldValue.arrayRemove(folder.children[index])
But this solution works only for the top level ;(
Does somebody know how to remove deeper Nested elements?
I tried:
docRef.update({[`children[${index}].children`]: firebase.firestore.FieldValue.arrayRemove(
folder.children[index].children[secondIndex])});
But it throws an Error (Paths must not contain '~', '*', '/', '[', or ']')
Thanks for your help ;)

Firestore does not support modifying array items by index. FieldValue.arrayRemove only works if you pass the exact contents of the data to remove from an array field. If you only know the index, then what you'll have to do is read the document, modify the array in memory, then write the new document contents back.

How to create dynamic nested accordion in React Native

All of the examples I've found online only show how to create single level accordion, like this:
-parent1
-child1
-parent2
-child2
I need to create dynamic accordion that has multiple nested parents, like this:
-parent
-subparent1
-subparent2
...
-subparentN
- child
My data comes in this format:
// first object in response is always considered to be the PARENT,
last one is always CHILD, and those in between are SUBPARENTS
// number of SUBPARENTS is not constant
"parents": [
{
"id": "583", // TOP LEVEL PARENT
"label": "PARENT",
"description": "irrelevant description here, i only need to show label for parents"
},
{
"id": "593",
"label": "SUBPARENT1",
"description": "..."
},
{
"id": "594",
"label": "SUBPARENT2",
"description": "..."
},
{
"id": "604",
"label": "SUBPARENT3",
"description": "..."
},
{
"id": "605", // CHILD
"label": "CHILD LABEL",
"description": "FEW LINES OF DESCRIPTION I NEED TO DISPLAY"
}
]

Based on the component you linked, it might be a good idea to have each as its own array (parent, subparent, an child label), and render its own collapsible.
For parent, have an accordion inside _renderContent function, and have that accordion be filled with its subparent. For subparent with child, have their _renderContent be filled with its child's content as well.
For parent's renderContent (see its sections props)
_renderContent = section => {
return (
<View style={styles.content}>
<Accordion
sections={SUBPARENT_SECTIONS}
activeSections={this.state.activeSections}
renderSectionTitle={this._renderSectionTitle}
renderHeader={this._renderHeader}
renderContent={this._renderContent}
onChange={this._updateSections}
/>
</View>
);
};
For subparent, do the same thing with its child label. It's probably a good idea not to have them on the same array, so you don't confuse them together.

React element - array objects only returning first item?

I am trying to retrieve item values from an object containing several items. The object is an array object. I am puzzled by only being able to retrive the first item and its values in each array instead of all items. Can anybody tell me what I am missing here.
The array object example:
{ "ITEM 1": [
{
"id": 123,
"name": "item1a"
},
{
"id": 234,
"name": "item1b"
},
{
"id": 345,
"name": "item1c"
}
],
"ITEM 2": [
{
"id": 456,
"name": "item2a"
},
{
"id": 567,
"name": "item2b"
},
{
"id": 678,
"name": "item2c"
}],
}
I have data within the new element and on debugging see that loop flows correctly but for some reason only the first item is rendered.
My code that is wrapped in an html element is as follows:
{ Object.keys(this.props.data).map(function (key) {
var list = component.props.data[key];
for (i = 0; i < facetParent.length; i++) {
var item = list[i];
return (
<CheckBox
key={item.id}
data={item}
name={item.name} />
)
}}, this)}
Any suggestions are much appreciated.

The return function immediately terminates the function execution. That is why you only get the first item. Depending on what version of react you use, you should create 2 arrays and join them before rendering

MongoDb: How to get a field (sub document) from a document?

Consider this example collection:
{
"_id:"0,
"firstname":"Tom",
"children" : {
"childA":{
"toys":{
'toy 1':'batman',
'toy 2':'car',
'toy 3':'train',
}
"movies": {
'movie 1': "Ironman"
'movie 2': "Deathwish"
}
},
"childB":{
"toys":{
'toy 1':'doll',
'toy 2':'bike',
'toy 3':'xbox',
}
"movies": {
'movie 1': "Frozen"
'movie 2': "Barbie"
}
}
}
}
Now I would like to retrieve ONLY the movies from a particular document.
I have tried something like this:
movies = users.find_one({'_id': 0}, {'_id': 0, 'children.ChildA.movies': 1})
However, I get the whole field structure from 'children' down to 'movies' and it's content. How do I just do a query and retrieve only the content of 'movies'?
To be specific I want to end up with this:
{
'movie 1': "Frozen"
'movie 2': "Barbie"
}

The problem here is your current data structure is not really great for querying. This is mostly because you are using "keys" to actually represent "data points", and while it might initially seem to be a logical idea it is actually a very bad practice.
So rather than do something like assign "childA" and "childB" as keys of an object or "sub-document", you are better off assigning these are "values" to a generic key name in a structure like this:
{
"_id:"0,
"firstname":"Tom",
"children" : [
{
"name": "childA",
"toys": [
"batman",
"car",
"train"
],
"movies": [
"Ironman"
"Deathwish"
]
},
{
"name": "childB",
"toys": [
"doll",
"bike",
"xbox",
],
"movies": [
"Frozen",
"Barbie"
]
}
]
}
Not the best as there are nested arrays, which can be a potential problem but there are workarounds to this as well ( but later ), but the main point here is this is a lot better than defining the data in "keys". And the main problem with "keys" that are not consistently named is that MongoDB does not generally allow any way to "wildcard" these names, so you are stuck with naming and "absolute path" in order to access elements as in:
children -> childA -> toys
children -> childB -> toys
And that in a nutshell is bad, and compared to this:
"children.toys"
From the sample prepared above, then I would say that is a whole lot better approach to organizing your data.
Even so, just getting back something such as a "unique list of movies" is out of scope for standard .find() type queries in MongoDB. This actually requires something more of "document manipulation" and is well supported in the aggregation framework for MongoDB. This has extensive capabilities for manipulation that is not present in the query methods, and as a per document response with the above structure then you can do this:
db.collection.aggregate([
# De-normalize the array content first
{ "$unwind": "$children" },
# De-normalize the content from the inner array as well
{ "$unwind": "$children.movies" },
# Group back, well optionally, but just the "movies" per document
{ "$group": {
"_id": "$_id",
"movies": { "$addToSet": "$children.movies" }
}}
])
So now the "list" response in the document only contains the "unique" movies, which corresponds more to what you are asking. Alternately you could just $push instead and make a "non-unique" list. But stupidly that is actually the same as this:
db.collection.find({},{ "_id": False, "children.movies": True })
As a "collection wide" concept, then you could simplify this a lot by simply using the .distinct() method. Which basically forms a list of "distinct" keys based on the input you provide. This playes with arrays really well:
db.collection.distinct("children.toys")
And that is essentially a collection wide analysis of all the "distinct" occurrences for each"toys" value in the collection, and returned as a simple "array".
But as for you existing structure, it deserves a solution to explain, but you really must understand that the explanation is horrible. The problem here is that the "native" and optimized methods available to general queries and aggregation methods are not available at all and the only option available is JavaScript based processing. Which even though a little better through "v8" engine integration, is still really a complete slouch when compared side by side with native code methods.
So from the "original" form that you have, ( JavaScript form, functions have to be so easy to translate") :
db.collection.mapReduce(
// Mapper
function() {
var id this._id;
children = this.children;
Object.keys(children).forEach(function(child) {
Object.keys(child).forEach(function(childKey) {
Object.keys(childKey).forEach(function(toy) {
emit(
id, { "toys": [children[childkey]["toys"][toy]] }
);
});
});
});
},
// Reducer
function(key,values) {
var output = { "toys": [] };
values.forEach(function(value) {
value.toys.forEach(function(toy) {
if ( ouput.toys.indexOf( toy ) == -1 )
output.toys.push( toy );
});
});
},
{
"out": { "inline": 1 }
}
)
So JavaScript evaluation is the "horrible" approach as this is much slower in execution, and you see the "traversing" code that needs to be implemented. Bad news for performance, so don't do it. Change the structure instead.
As a final part, you could model this differently to avoid the "nested array" concept. And understand that the only real problem with a "nested array" is that "updating" a nested element is really impossible without reading in the whole document and modifying it.
So $push and $pull methods work fine. But using a "positional" $ operator just does not work as the "outer" array index is always the "first" matched element. So if this really was a problem for you then you could do something like this, for example:
{
"_id:"0,
"firstname":"Tom",
"childtoys" : [
{
"name": "childA",
"toy": "batman"
}.
{
"name": "childA",
"toy": "car"
},
{
"name": "childA",
"toy": "train"
},
{
"name": "childB",
"toy": "doll"
},
{
"name": "childB",
"toy": "bike"
},
{
"name": "childB",
"toy": "xbox"
}
],
"childMovies": [
{
"name": "childA"
"movie": "Ironman"
},
{
"name": "childA",
"movie": "Deathwish"
},
{
"name": "childB",
"movie": "Frozen"
},
{
"name": "childB",
"movie": "Barbie"
}
]
}
That would be one way to avoid the problem with nested updates if you did indeed need to "update" items on a regular basis rather than just $push and $pull items to the "toys" and "movies" arrays.
But the overall message here is to design your data around the access patterns you actually use. MongoDB does generally not like things with a "strict path" in the terms of being able to query or otherwise flexibly issue updates.

Projections in MongoDB make use of '1' and '0' , not 'True'/'False'.
Moreover ensure that the fields are specified in the right cases(uppercase/lowercase)
The query should be as below:
db.users.findOne({'_id': 0}, {'_id': 0, 'children.childA.movies': 1})
Which will result in :
{
"children" : {
"childA" : {
"movies" : {
"movie 1" : "Ironman",
"movie 2" : "Deathwish"
}
}
}
}

Populate AngularJS {{expression}} within ng-repeat using a second array

I'm completely rebuilding my website (originally hacked together with Wordpress) using Laravel and AngularJS. It's been a massive learning experience and I think I'm nearly there but for one problem.
On my site 'schemes' (or courses) are made up of 'units' which are made up of 'lessons'. Retrieving this data is fine, using Eloquent I retrieve valid JSON like this made up example...
[
{
"id": "1", //Scheme Id
"title": "Sports",
"description": "This is a Sports course!",
"units": [
{
"id": "1",
"title": "Tennis",
"lessons": [
{
"id": "6",
"title": "Serving"
},
{
"id": "7",
"title": "Hitting the ball with top-spin"
}
]
},
{
"id": "2",
"title": "Athletics",
"lessons": [
{
"id": "1",
"title": "Long Jump"
},
{
"id": "2",
"title": "Hurdling Technique"
}
]
},
{
"id": "4",
"title": "Golf",
"lessons": [
{
"id": "4",
"title": "Pitching"
},
{
"id": "5",
"title": "Putting"
}
]
}
]
}
....
]
Separately I have a simple array of completed lesson ids for a particular user like this...
[2, 6, 8, 9] ///User has completed lessons with ids of 2,6,8 and 9
In my view I'm using nested ng-repeat loops like so...
...
<div ng-controller="SchemesController">
<div ng-repeat="scheme in schemes">
<h1>{{scheme.title}}</h1>
<div ng-repeat="unit in scheme.units">
<h3>{{unit.title}}</h3>
<div ng-repeat="lesson in unit.lessons">
<div>{{lesson.title}}: {{status}}</div>
</div>
</div>
</div>
</div><!--[end of ng-controller="SchemesController"]-->
....
SchemesController (v simple!) looks like this...
var app = angular.module('schemesApp', []);
app.controller('SchemesController', function($scope){
$scope.schemes=jsonData;
});
The problem is I have no idea how to populate the {{status}} field which I want to state simply 'Complete' or 'Incomplete. I investigated whether I could somehow add this info to my original array like this...
"lessons": [
{
"id": "6",
"title": "Serving",
"status": "Complete" //populated somehow
},
{
"id": "7",
"title": "Hitting the ball with top-spin",
}
]
but I got nowhere slowly. Is there a way to do this (I've played around with underscore.js and felt this could help?).
Or do I populate {{status}} from creating and calling a javascript function?!?
ANY help that anyone could offer would be incredible. I'm a school teacher and for some sadistic reason I find a bit of programming/web design a fun use of my spare time so I apologise if this is a stupid question. THANKS in advance!!!
btw if anyone has a better 'title' for this question then please let me know.

I'm assuming you don't need to persist the status back to the database...
This is where you're having the problem:
<div>{{lesson.title}}: {{status}}</div>
You really don't need to store the status in your data model, because it's just used for presentation purposes.
Let's say your array of completed lessons is defined like this:
$scope.completedLessons = [1, 2, 3, 4, 5] // Or however you'd assign it
You need to create a function in your scope like this:
$scope.isLessonCompleted = function(lessonId) {
return $scope.completedLessons.indexOf(lessonId) > -1;
};
Then you need to change the html from above to this:
<div>{{lesson.title}}: {{isLessonCompleted(lesson.id) && 'Complete' || 'Incomplete'}}</div>

If lessons are also a model and each lesson should have a status, which isn't a column/field in your table but is something you'll add logic to determine, you could add a custom model accessor by adding the following to your models/Lesson.php:
// Append custom accessor attributes
protected $appends = ['status'];
public function getStatusAttribute() {
// Add logic here
return 'Complete';
}
This way, when you use Eloquent to retrieve your data, you'll also see a status attribute as part of the object, so you could then access it as usual $lesson->status (PHP) or lesson.status (JS).
For more information, see the official Laravel documentation on accessors and mutators