Loopback v.4 is relatively new and I couldn't find how to modify the name of the mongodb collection here on stackoverflow.
after sometime (try and error), found out that the collection name is exactly your model name.
the structure of the loopback 4 as far as i know:
models
yourmodel.model.ts
datasources
yourdatasource.datasource.ts
yourdatasource.datasource.json
controllers
repositories
i think it would be nice if they add the collection name as a field to the json file in datasource directory, since it already includes the configuration for the mongodb.
hope this helps. thought it would be nice to have this on Stackoverflow. Please feel free to add to this answer, so it would cover more edge cases.
Related
Following
Loobback Docs: Discovering models from relational databases, Stackoverflow answer: Loopback not discovering models and Loopback datasource juggler API: Datasource I created a discover js script to get models from an oracle database. The problem is that it never managed to read the relations from the tables. I used the methods
discoverAndBuildModels - The result object had the properties of the table and an array called relations but that array was empty
discoverSchema - I managed to get the actual model JSON file and write it to the appropriate location. As the method is described in the api to not read relations i was not surprised to not find any here
discoverSchemas - Includes option to read relations (called relations but also tried it with associations) which gave me a similar result than discoverSchema but the "relations" tag only had an empty json object assigned to it.
I tried all options with a variety of relations and associations settings but none of them gave me anything but an empty object as the "relations" tag.
Am I missing something in the setup?
Oh boy, we've also had this issue. You just have to make sure that your user has the appropriated rights. Choose a privileged user (maybe admin?) to gather the data and it should work.
Check out this question for reference: How to query the permissions on an Oracle directory?
during the development of my app, i very often add custom and new fields to an existing schema, making the 'old' content in my mongodb 'incompelete' and missing the new fields. this leads sometimes to null content where it's required and it's in my use case very bad.
my question is what command/utility do i need to use to make mongoose validate my old documents, and in potential add those missing fields with pre-defined defaults to the old documents?
i remember reading something about that kind of functionality when i started learning how to use mongoose, but i just can't find it anywhere anymore..
thanks in advance :)
Amit
I have an issue of replication and I need your help in it.In couchDb replication,I want to replicate in such a way that during Couchdb replication I want to reset/update some specific attributes of a a document for some purpose and then these edited documents should be saved in replicated db without effecting the original ones.For example:
A document named Student with attributes id,name,class etc.
And I want to replicate this document in the way that its name and class should be reset/updated.
Will you please tell me how can I achieve it.
Thanks.
You can't update docs during the replication.
But you can exclude docs from being replicated with the help of a CouchDB filter (e.g. preventing all docs with a revision higher then 1 from being replicated).
If you want to have multiple versions of the same dataset (e.g. to have dataset revisions) - i use the term "dataset" instead of "doc" to clearly express that not the internal CouchDB doc revision handling is involved - you have to store them as separated docs that have all a unique id and a reference property like original: "UUID_of_the_original".
you can't use the CouchDB doc revision handling for that purpose (thats what many people think when they see the _rev property in the docs)
I am looking at the documentation for Meteor and it gives a few examples. I'm a bit confused about two things: First, where do you build the db (keeping security in mind)? Do I keep it all in the server/private folder to restrict client-side access? And second, how do I define the structure? For example, the code they show:
Rooms = new Meteor.Collection("rooms");
Messages = new Meteor.Collection("messages");
Parties = new Meteor.Collection("parties");
Rooms.insert({name: "Conference Room A"});
var myRooms = Rooms.find({}).fetch();
Messages.insert({text: "Hello world", room: myRooms[0]._id});
Parties.insert({name: "Super Bowl Party"});
I don't understand how a collection's structure is defined. Are they just able to define a collection and throw arbitrary data into it?
To answer your first question about where to put the new Meteor.Collection statements, they should go in a .js file in a folder accessible by both client and server, such as /collections. (With some exceptions: any collections that are never synced to the client, like server logs, should be defined inside /server somewhere; and any local collections should be defined in client code.)
As for your second question about structure: MongoDB is a document database, which by definition has no structure. Per the docs:
A database holds a set of collections. A collection holds a set of
documents. A document is a set of key-value pairs. Documents have
dynamic schema. Dynamic schema means that documents in the same
collection do not need to have the same set of fields or structure,
and common fields in a collection’s documents may hold different types
of data.
You may also have heard this called NoSQL. Each document (record in SQL parlance) can have different fields. Hence, there's no place where you define initial structure for a collection; each document gets its "structure" defined when it's inserted or updated.
In practice, I like to create a block comment above each new Meteor.Collection statement explaining what I intend the structure to be for most or all documents in that collection, so I have something to refer to later on when I insert or update the collection's documents. But it's up to me in those insert or update functions to follow whatever structure I define for myself.
A good practice would probably be defining your collection on both client and server with a single bit of javascript code. In other words, put the following
MyCollection = new Meteor.Collection("rooms");
// ...
anywhere but neither in the client nor in the server directory. Note that this directive alone does not expose any sensitive data to nobody.
A brand new meteor project would contain by default the insecure and autopublish packages. The former will basically allow any client to alter your database in every possible way, i.e. insert, update and remove documents. The latter will make sure that all database content is published to everyone, no matter how ridiculously this may sound. But fear not! Their only goal is to simplify the development process at the very early stage. You should get rid of these to guys from your project as soon as you start considering security issues of any kind.
As soon as the insecure package is removed from your project you can control the database privileges by defining MyCollection.allow and MyCollection.deny rules. Please check the documentation for more details. The only thing I would like to mention here is that this code should probably be considered as a sensitive one, so I guess you should put it into your server directory.
Removing the autopublish package has effect on the set of data that will be sent to your clients. Again you can control it and define privilages of your choice by implementing a custom Meteor.publish routine. This is all documented here. Here, you have no option. The code can only run in the server environment, so the best choice would be to put it in the server directory.
About your second question. The whole buzz about NoSQL databases (like mongodb) is to put as few restrictions on the structure of your database as possible. In other words, how the collections are structured is only up to you. You don't have to define no models and you can change the structure of your documents (and or remove fields) any time you want. Doesn't it sound great? :)
Total newbie question now... Suffice to say, I have searched for a completely noddy explanation but have not found anything 'dumb' enough. The problem is...
I have created a core data stack in which I have a entity called 'Client' and an entity called 'Car'. It is a one-to-many relationship.
So far i have successfully created and fetched the client list using code from apple's tutorial. Once I select a client, I then push a new tableViewController which should list the Cars for that chosen client.
First question...
I am used to sql style database programming where if I wanted to add a car to a client, I would simply add a 'ClientID' tag to the 'Car' record thereby providing the relationship to a specific client. How do I do the equivalent in core data? My understanding from my reading is adding attributes to point to other entities isnt necessary - core data maintains this relationship for you without needing additional attributes in the entities.
Second question...
As and when I have created a 'car' entity and successfully linked it to a 'Client'. How to I create a fetch which will retrieve just THAT client's cars. I could alter the code from apple to fetch ALL cars but I don't know how to fetch cars associated with a given client. From my reading, I think I need to use predicates, but apples predicate documentation stands alone and does not give clear guidance on how to use it with core data
I realise how noddy this is, but I cant find an idiots guide anywhere...
Any help/code exmaples much appreciated.
OK, I have answered my own question. For those who have found my question and would like to know the answer, it is extremely simple...
Firstly, to create a 'Car' and associate it with a 'Client'. Firstly create a 'Car' as you normally would and simply add this line of code...
newCar.client = client;
This sets the 'client' relationship on the 'Car' record to the client in question.
Secondly, I had thought that if you had a client and needed to find their cars, you would need a new fetch. But not so! Simply use the following lines of code...
NSSet *cars = client.cars;
[self setCarsArray:[cars allObjects]];
The first line uses "client.cars" o follow the object graph to determine the cars this client has and populates them in an NSSet. The second line then populates a NSArray which is declared in the current viewcontroller which can be used to for display purposes.
Sorted!!