> For the complete documentation index, see [llms.txt](https://coldbox-validation.ortusbooks.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://coldbox-validation.ortusbooks.com/v1.x/overview/declaring-constraints/domain-object.md).

# Domain Object

Within any domain object you can define a public variable called `constraints` that is a assigned an implicit structure of validation rules for any fields or properties in your object.

### Declaration

{% code title="models/User.cfc" %}

```javascript
component persistent="true"{

    // Object properties
    property name="id" fieldtype="id" generator="native" setter="false";
    property name="fname";
    property name="lname";
    property name="email";
    property name="username";
    property name="password";
    property name="age";

    // Validation
    this.constraints = {
        // Constraints go here
    }
}
```

{% endcode %}

We can then create the validation rules for the properties it will apply to it:

{% code title="config/User.cfc" %}

```javascript
component persistent="true"{

    ...

    // Validation
    this.constraints = {
        fname = { required = true },
        lname = { required = true},
        username = {required=true, size="6..10"},
        password = {required=true, size="6..8"},
        email = {required=true, type="email"},
        age = {required=true, type="numeric", min=18}
    };
}
```

{% endcode %}

That easy! You can just declare these validation rules and ColdBox will validate your properties according to the rules. In this case you can see that a password must be between 6 and 10 characters long, and it cannot be blank.

{% hint style="info" %}
By default all properties are of type **string** and **not** required
{% endhint %}

### Usage

You can then use them implicitly

```javascript
validate( myUser );
```


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation by asking a question.

Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters:

```
GET https://coldbox-validation.ortusbooks.com/v1.x/overview/declaring-constraints/domain-object.md?ask=<question>&goal=<user_goal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.