How I add a dynamic url field to an attachment model?

[bylly1]

Hello I m struggling to implement a dynamic field to a model and I don t know how to do it. Here I my model:

const attachmentSchema = new Schema<AttachmentProps>(
	{
		filename: { type: String },
                filePath: { type: String },
		mimeType: { type: String },
		size: { type: Number },
);

I need when I get the collection to add a extra field named url which should be like this

url = `${req.protocol}://${req.get("host")}/media${doc.filePath}`; 

I don t want to save the url inside database becase maybe I want to change the host in the future and I don t want to store it.

Right know I implemented a solution inside controller but I don t like it too much:

     const example = await ExampleModel.findOne(query).populate(
        {
		path: "file",
		transform: (doc) => {
		if (doc) {
			// Set the url dynamically
			doc.url = `${req.protocol}://${req.get("host")}/media${doc.filePath}`;
		}
		return doc;
		},
		select: "url filePath fileName mimeType",
        }
     )

but I m not too happy about this solution. can anybody know a better solution?

[DIEGOHORVATTI]

Hello I m struggling to implement a dynamic field to a model and I don t know how to do it. Here I my model:

const attachmentSchema = new Schema<AttachmentProps>(
	{
		filename: { type: String },
                filePath: { type: String },
		mimeType: { type: String },
		size: { type: Number },
);

I need when I get the collection to add a extra field named url which should be like this

url = `${req.protocol}://${req.get("host")}/media${doc.filePath}`; 

I don t want to save the url inside database becase maybe I want to change the host in the future and I don t want to store it.

Right know I implemented a solution inside controller but I don t like it too much:

     const example = await ExampleModel.findOne(query).populate(
        {
		path: "file",
		transform: (doc) => {
		if (doc) {
			// Set the url dynamically
			doc.url = `${req.protocol}://${req.get("host")}/media${doc.filePath}`;
		}
		return doc;
		},
		select: "url filePath fileName mimeType",
        }
     )

but I m not too happy about this solution. can anybody know a better solution?

const mongoose = require("mongoose");
const { Schema } = mongoose;

const attachmentSchema = new Schema(
  {
    filename: { type: String },
    filePath: { type: String },
    mimeType: { type: String },
    size: { type: Number },
  },
  {
    toJSON: { virtuals: true },
    toObject: { virtuals: true },
  }
);

// Virtual for the URL
attachmentSchema.virtual("url").get(function () {
  return `${this.protocol}://${this.host}/media${this.filePath}`;
});

// Middleware to attach the request context
attachmentSchema.pre("find", function () {
  const req = this.options?.req;
  if (req) {
    this.protocol = req.protocol;
    this.host = req.get("host");
  }
});

const AttachmentModel = mongoose.model("Attachment", attachmentSchema);

// Usage in a controller
const getExample = async (req, res) => {
  const example = await ExampleModel.findOne(query)
    .populate({
      path: "file",
      select: "url filePath filename mimeType",
    })
    .setOptions({ req });

  res.json(example);
};