Adding field to schema using mongoose in node js - node.js

Question

I am trying to write a schema that takes the parameters required by an activity. I am want to add a field 'activityParameters' that will be case specific depending on the activityType. Suppose if the activityType is email then the activityParameters should store details like'to:String, from:String, subject: String, body: String' and if the activity is "export" then it should store parameters like 'path:String' . Different types of activity will have different parameters. Please help me how to do this.
var activity_type = {
values: 'email export'.split(' '),
message: 'validation failed for path `{PATH}` with value `{VALUE}`'
};
var activitySchema = new Schema({
activityName: String,
activityDescription: String,
executionTime: {type: Date , default: null},
activityStartTime: {type: Date , default: null},
activityCompletionTime: {type: Date , default: null},
activityType: {type:String, enum: activity_type},
//activityParameters: ,
appName : String,
activityRetryCount: {type:Number,default:0},
createdOn: {type:Date , default:Date.now},
deletedOn: {type: Date , default: null},
updatedOn: {type: Date , default: null}
});

Answer 1

There's really no good answer for doing this with mongoose and maintaining a strongly typed schema.
You can specify all the fields for each type on the schema and then use them depending on type (export vs message).
var activitySchema = new Schema({
...
activityParameters: {
to:String,
from:String,
path:String
}});
You might consider having a key per subtype to be an improvement:
var activitySchema = new Schema({
...
emailActivityParameters:{
to:String,
from:String,
},
exportActivityParameters:{
path:String,
}
});
It would be pretty easy to access each "subdocument" depending on the activity type.
Finally, you can have a key called activityParameters and have that be freeform json:
var activitySchema = new Schema({
...
activityParameters: {}
});
In this case you can preserve your schema integrity using custom validators.
If these approaches don't appeal then maybe mongoose isn't the right tool you. You could use a lower level mongo driver and then something like Typescript or json schema to validate your models before you save them to mongoose. Check out this, for example: https://github.com/litixsoft/lx-valid.