I’d like to dynamically attach a schema to a particular field, based on some

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Asked: June 4, 20262026-06-04T18:21:40+00:00 2026-06-04T18:21:40+00:00

I’d like to dynamically attach a schema to a particular field, based on some

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I’d like to dynamically attach a schema to a particular field, based on some business logic in schema.pre('save',function(..){...}). How to do this, if at all possible?

Some (simplified) schemas and background:

var fact= new Schema({  
    name: { type: String, required: true, index: { unique: false }}
    ,value: {type:  {}, required: true}  
    ,moreinfodesc: { type: String, required: false} 
    ,createddate : { type: Date, required: true, default: Date.now, select: false } }
}, { collection: 'Fact' } );

var factSchema= new Schema({
    name: { type: String, required: true, index: { unique: true }}
    , valueType: { type: {}, required: true}                                        
    ,isMulti: {type: Boolean, required: true }

    //ACL-stuff
    ,directChangeRoles: {type: [String]} //i.e: [super, admin,owner]
    ,suggestChangeRoles: {type: [String]} //ie: [editor]
    ,enum: {type: [{}]} 
    ,mixins: {type: [String]} 
}, { collection: 'FactSchema' });

This is a simplified structure to allow “facts’ of a particular ‘entity’ to be edited.

e.g: entityA.facts=[fact]

As can be seen from the schema’s fact.value can have any type as far as mongoose is concerned. I however, want to constrain it at runtime to the schema as defined in
FactSchema.valueType (a String containing “Boolean”, “String” or something more complex as “[Tag]”) . This might all seem cumbersome, but this is the way i’d like to go for several reasons.

So let’s say that for a particular fact with fact.name=tags I want to assign fact.value the type [Tag] at runtime. For this I would have setup a Tag-schema with validation like usual and have fact.value validate against it.

I was thinking of somehow “attaching” the [Tag]-schema to fact.value in fact.pre('save',function(..){.. //validation here }) and hope validation would magically happen as if fact.valuewas assigned the type [Tag] at design-time instead of run-time.

Finally the question: I’ve got no idea if it’s possible to do that ‘attach’ and if so, how?

Thanks.