How to realize multi level chain call

[LeonYanghaha]

I think mongoose find function is very good, it can Cat.find({name:"leon"}).populate("path").sort({"field": - 1}).skip (0).limit (10).lean(); this chain call is very easy to use, but now I have a problem. I want to encapsulate the find function myself. How can I encapsulate it? I don't know how to encapsulate it. I know return this is a good idea, but what should I return here? I want someone to give me some ideas? Thank you for your help.

This is my code now. What should I do next. How can I write it?

 async find(options: Object, populate?: string) {

    if (!populate) {
      return await this.mappingModel(meta.collections).find(options);
    }

    if (typeof populate === "string" && populate !== "") {
      return await this.mappingModel(meta.collections).find(options).populate(populate);
    }
    throw Error("Multi level chained calls are not supported ");
    // TODO 2020/11/27 15:09    How to realize multi level chain call
  }

[AbdelrahmanHafez]

It's a good idea to encapsulate 3rd-party code with your own code, it helps with testing, and makes things easier if you want to change libraries in the future.

Assuming this.mappingModel(meta.collections) returns a mongoose model, you could do the following.

module.exports = {
  async find({ filter, populate, skip, limit, sort }) {
    return await this.mappingModel(meta.collections)
      .find(filter)
      .populate(populate)
      .skip(skip)
      .limit(limit)
      .sort(sort);
  }
};

Notice how the code doesn't do any checks for whether populate/skip/limit/sort are present or not, because mongoose is smart enough to ignore the .populate if it's passed an empty value, same goes for the rest of the chain.

I am not sure what you mean by "multi level chain call", can you elaborate on that?

[LeonYanghaha]

Your answer is very good, perfectly solved my problem. Thank you.

[AbdelrahmanHafez]

Happy to help.

[vkarpov15]

It sounds like you might be looking for custom query methods, that lets you add custom helpers like so:

catSchema.query.byName = function(name) {
  return this.find({name: name}).populate("path").sort({"field": - 1}).skip(0).limit(10).lean();
};

You can then use byName() with chaining, like Cat.find().byName('leon').select('name path')