Definitelytyped: [@types/mongoose] Support for loadClass()

[lonix1]

If you know how to fix the issue, make a pull request instead.

• [x] I tried using the @types/xxxx package and had problems.
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  • Authors: @simonxca @horiuchi @sindrenm @lukasz-zak @Alorel @jendrikw @ethanresnick @vologab @Ethan @vologa @jussikinnula @ondratra @alfirin @idandrd @dominikh @Fazendaaa @NormanPerrin @danmana @stablio
  
  

Mongoose now allows loading behavior from an ES6 class into the schema using MySchema.loadClass(MyClass);

This seems to work, but within the class the schema's properties obviously cannot be found.

class MyClass { public foo() { console.log(this.bar); } // this.bar cannot be found, intellisense complains, warnings, etc. }

I'm not sure how to deal with this other than allowing the warnings. If this cannot be addressed, at least maybe we can get a new section for it in the README.md explaining how to use it?

[jendrikw]

The solution is to annotate each function in the class with a this parameter, which tells typescript what this refers to when the function is called.

class UserClass {
    getFullName(this: IUser) {
        return `${this.firstName} ${this.lastName}`;
   }
}

[lonix1]

@jendrikw Thanks that works!

I actually discovered that if I change from class MyClass { } to class MyClass extends mongoose.Model { } then the problem goes away. But your solution is more accurate and I get full intellisense as well!

I guess this is not a bug. But it should be in the docs, it's so useful.

[jendrikw]

For the record, your code typechecks because Model has a construct signature of new(doc?: any): T; with T defaulting to any. The result is that you can access any property of this.