What is Instance Method? Means, Instance Method = Instance+Method here Instance means, example, class Parent { ...... ..... } const mother = new Parent(....) // here, mother is instance of Parent.
Means, Instance Method is a instance of Class + some methods
Example,
const user = new User(payload); // Here, User is class and user is instance of that class await user.save(); // here, user is a instance and save is a method. this means user.save() is an instance method. this instance method is builtin.
Let's create a custom instance method //1. create an interface for methods export interface IUserMethods { fullName(): string; }
//2. Create a new Model type that knows about IUserMethods... type UserModel = Model<IUser, {}, IUserMethods>;
//3. Pass IUser, UserModel, and IUserMethods in schema const userSchema = new Schema<IUser, UserModel, IUserMethods>({ ....... .......
//4. Now, I have to write function definition like this userSchema.method("fullName", function fullName() { return ( this.name.firstName + " " + this.name.middleName + " " + this.name.lastName ); }); });
//5. I have to pass that UserModel in User model generic as a parameter. like this const User = model<IUser, UserModel>("User", userSchema);
//6. Now I can use fullname function with the help of instance of User model, like this console.log(user.fullName())
Summery of the instance method is, Instance method is only work when I create a instance with the help of model
What is static in Class? Static is a attached methods of class, which i can directly call with That class( not instance of class). // Example Class => Attached --> Methods -->Directly call using class
Example for instance, const user = new User() user.fullName()
Example for Static User.fullName()
How to Implement both Static and Method?
- make interface
// Static + Method
export interface UserModel extends Model {
getAdminUsers(): Promise>;
}
- In model file, I have to replace instance method's UserModel with that UserModel import { IUser, IUserMethods, UserModel } from "./user.interface";
// type UserModel = Model<IUser, {}, IUserMethods>;
const userSchema = new Schema<IUser, UserModel, IUserMethods>({
.....
..........
..........
});
- Then, using static method we can directly access using this and make a database query
userSchema.static("getAdminUsers", async function getAdminUsers() {
const admins = await this.find({ role: "admin" });
return admins
});
-
Now, I can easily use getAdminUsers method to get all admin from services file. like this
// get user by id from db export const getAdminUsersFromDB = async () => { const admins = await User.getAdminUsers();return admins; };