# `Zoi.Schema`
[🔗](https://github.com/phcurado/zoi/blob/v0.17.4/lib/zoi/schema.ex#L1)

Utilities for traversing and transforming Zoi schemas.

This module provides functions to recursively walk through schema structures
and apply transformations. This is useful for applying defaults, enabling
features like coercion, or wrapping types across an entire schema tree.

The traversal is post-order, meaning child nodes are transformed before their
parents, allowing transformations to work with already-processed nested schemas.

## Examples

    # Enable coercion on all types
    schema = Zoi.map(%{
      name: Zoi.string(),
      age: Zoi.integer()
    })
    |> Zoi.Schema.traverse(&Zoi.coerce/1)

    # Apply nullish to all fields
    schema
    |> Zoi.Schema.traverse(&Zoi.nullish/1)

    # Conditional transformation based on field path
    schema = Zoi.map(%{
      password: Zoi.string(),
      email: Zoi.string()
    })
    |> Zoi.Schema.traverse(fn node, path ->
      if :password in path do
        node
      else
        Zoi.coerce(node)
      end
    end)

    # Chain multiple transformations
    schema
    |> Zoi.Schema.traverse(&Zoi.nullish/1)
    |> Zoi.Schema.traverse(&Zoi.coerce/1)

# `traverse`

```elixir
@spec traverse(Zoi.schema(), function()) :: Zoi.schema()
```

Traverses a schema tree and applies a transformation function to each node.

The traversal walks through nested schemas (objects, arrays, unions, maps, tuples, etc.)
and applies the transformation function to each child node. The root node is not transformed.

The transformation function receives the current node and optionally the path (list of field
keys showing the location in the schema tree, e.g., `[:user, :address, :street]`).

## Examples

    # Enable coercion on all nested fields
    schema
    |> Zoi.Schema.traverse(&Zoi.coerce/1)

    # Apply transformation conditionally using path
    schema
    |> Zoi.Schema.traverse(fn node, path ->
      if :password in path do
        node
      else
        Zoi.coerce(node)
      end
    end)

---

*Consult [api-reference.md](api-reference.md) for complete listing*