# leptos_form_tool
[](https://crates.io/crates/leptos_form_tool)
[](https://docs.rs/leptos_form_tool)
A declarative way to create forms for [leptos](https://leptos.dev/).
leptos_form_tool allows you to define forms in a declarative way.
Want a text box? Just call `.text_input` on the form builder. Then, separately,
you define a FormStyle to specify how that text box should be rendered.
This has several advantages:
- Separates the layout of the form from how it is rendered and styled
- Allows different styles to be swapped in and out quickly
## Validations
You might find yourself asking, but why not just use components?
The biggest reason for creating leptos_form_tool is support for
validating the fields. This validation logic can get rather complex, for
instance, you likely want to perform validation on the client when the user
clicks submit to immediately give the user feedback about any invalid input.
But you often also want to do the same validation on the server to protect
against any requests that don't come from your client or for a user that
doesn't have WASM enabled.
Additionally, you might want to change the validation of one control based
on the value of another. For example, you might want to make sure the "day"
field is in a valid range, but that range depends on what the user selects in
the "month" field. Or you might want to make sure the "confirm password" field
matches the "password" field. leptos_form_tool makes this easy, as the
validation function you provide operates on the entire form's data.
Sometimes you might not want to show some controls, and validation for those
controls should only be done when they are visible.
lepos_form_tool takes care of all this for you.
## FormStyle
To define how to render all the components a form might use, you define
a type that implements the `FormStyle` trait. This trait has a method for each
control that the form might need to render. To use this new style, you
just need to change the `Style` associated trait of your form to your new type.
It's actually a little more complicated than that...
To give custom styles a little more freedom to configure how to render their
controls on a per-control basis, the style will define an associated type
(usually an enum) called `StylingAttributes`. A styling attribute can be added
to a control by calling `.style(/* style */)` on the control builder. These
styling attributes are accessible to the `FormStyle` implementation when
rendering that control.
Therefore, swapping out styles also requires swapping out all the `.style()` calls.
## Builders
leptos_form_tool makes heavy use of the builder pattern. You will build the
form, controls, and sometimes even validation functions by calling methods on
a builder that constructs the object based on the values you give it.
## Context
Sometimes, you might want to be able to use something from the form's context
to render the form. For example, you may want to use a user's token as context,
to only render part of the form if they are an administrator. Or, you may
need to get the options for a certain drop-down dynamically. The form's context
is the solution to these problems.
On the form, you define the associated type `Context`. Then, any time you construct
a `Form`, you must provide that context. The context can be used in
the building of the form and can change what controls are rendered. Each control
builder function (ex. `.text_input()`) has a context variant
(ex. `.text_input_cx()`) that allows you to use the context
for building that control.
To avoid a whole lot of headaches, the context is immutable once passed into
the form. However, you can use leptos signals in the context just fine, as you don't
need mutable access to call get/set on the signal.
Since the context can change how the form is rendered, and what controls are
shown/hidden (thus changing what controls are validated), the context is
needed to validate the form data on the server side. In general, when
validating the form on the server, you should pass the same context as
you did on the client, to make sure the validation logic is the same.
If you are sure that changing the context won't change any of the validations,
it is ok to use different contexts on the server and client.
It is important to note that for controls that are not shown
(the `.show_when(/* condition */)` condition evaluates to `false`),
the validation for that field does not run.
## Custom Components
leptos_form_tool also supports custom components that can be defined in the
user space. This keeps leptos_form_tool from putting
limits on what you can do. There are `custom_*` methods on the form builder
that allow you to add your component.
## Getting Started
To learn by example, see the
[example project](https://github.com/MitchellMarinoDev/leptos_form_tool_example).
To follow a Getting Started guide, see [`getting_started.md`].
## Compatability
| form_tool version | leptos version |
| 0.2.0 | 0.6 |
## Contributing
To contribute, fork the repo and make a PR.
If you find a bug, feel free to open an issue.
By contributing, you agree that your changes are
subject to the license found in [`/LICENSE`].