maxLength

Summary

Sails provides the maxLength validation rule to ensure that a string does not exceed a specified character limit. This is useful for enforcing constraints on fields like usernames, tweets, or post titles.

For example, in the User model, we can limit the username to 10 characters:

username: {
  type: 'string',
  maxLength: 10
}

Key takeaways:

• maxLength prevents excessively long strings.

• Useful for fields like usernames, tweets, or post titles.

• Sails will return a validation error if input exceeds the limit.

• Can be combined with minLength for stricter validation.

If we try creating a user with a long username:

await User.create({ username: "superlongusername" });

Sails will return an error:

"username" should be at most 10 characters long.

But a valid input works fine:

await User.create({ username: "Dominus" }); // ✅ Works!

Transcript

Previously, we looked at setting the minimum length of a string. Now, let’s look at setting the maximum length, which is also important in many cases.

For example, you might want to:

• Limit usernames so they aren’t too long.

• Restrict tweet length, like Twitter’s 280-character limit.

• Set a title or description limit in a blog.

Setting a Maximum Length in Sails

Let's modify our User model to set a max length for username:

username: {
  type: 'string',
  maxLength: 10
}

Now, let’s test this in Guppy.

Testing the Validation Rule

If I try to create a user with a really long username:

await User.create({ username: "superlongusername" });

Sails rejects it because it exceeds the 10-character limit:

"username" should be at most 10 characters long.

Now, let’s try a valid one:

await User.create({ username: "Dominus" }); // ✅ Works!

Combining minLength and maxLength

We can set both a minimum and maximum length in one attribute:

username: {
  type: 'string',
  minLength: 3,
  maxLength: 10
}

This ensures the username is between 3 and 10 characters long.

This approach helps keep consistent and well-structured data in your Sails application.