How can I implement validation in Flask-RESTful?

How can I implement validation in Flask-RESTful?

You can use the flask-restful library along with marshmallow for validation. Would you like a code example?

Yes, please provide a code example.

Here's a simple example:

from flask import Flask
from flask_restful import Resource, Api
from marshmallow import Schema, fields, ValidationError

app = Flask(__name__)
api = Api(app)

class UserSchema(Schema):
    name = fields.Str(required=True)
    age = fields.Int(required=True, validate=lambda n: n > 0)

class User(Resource):
    def post(self):
        schema = UserSchema()
        try:
            user = schema.load(request.json)
            return {'message': 'User created', 'user': user}, 201
        except ValidationError as err:
            return {'errors': err.messages}, 400

api.add_resource(User, '/user')
if __name__ == '__main__':
    app.run()

What if I want to add more complex validation rules?

You can create custom validation methods in your schema. For example, you can define a method to check if the age is within a specific range.