# Implicit Transformers

In this guide, we'll review two new built in transformers added in ShapeShift version 0.0.7, `ImplicitMappingTransformer` and `ImplicitCollectionMappingTransformer`.

## ImplicitMappingTransformer

ImplicitMappingTransformer is used to transform subclasses mapped with ShapeShift. Lets look at the following example:

We have mapped `Address` class to its display class `AddressDisplay`.

{% tabs %}
{% tab title="Kotlin" %}

```kotlin
@DefaultMappingTarget(AddressDisplay::class)
class Address {
    @MappedField
    var country: String? = null

    @MappedField
    var city: String? = null

    @MappedField
    var address: String? = null
}

class AddressDisplay {
    var country: String? = null
    var city: String? = null
    var address: String? = null
}
```

{% endtab %}

{% tab title="Java" %}

```java
@DefaultMappingTarget(AddressDisplay::class)
public class Address {
    @MappedField
    private String country;

    @MappedField
    private String city;

    @MappedField
    private String address;

    // Getters and Setters...
}

public class AddressDisplay {
    private String country;
    private String city;
    private String address;

    // Getters and Setters...
}
```

{% endtab %}
{% endtabs %}

We can use ShapeShift to map `Address` to `AddressDisplay`. But what we do if `Address` is a subclass? We use the `ImplicitMappingTransformer`.

{% tabs %}
{% tab title="Kotlin" %}

```kotlin
@DefaultMappingTarget(UserDisplay::class)
class User {
    @MappedField
    var name: String? = null

    @MappedField(transformer = ImplicitMappingTransformer::class)
    var address: Address? = null
}

class UserDisplay {
    var name: String? = null
    var address: AddressDisplay? = null
}
```

{% endtab %}

{% tab title="Java" %}

```java
@DefaultMappingTarget(UserDisplay::class)
public class User {
    @MappedField
    private String name;

    @MappedField(transformer = ImplicitMappingTransformer.class)
    private Address address;

    // Getters and Setters...
}

public class UserDisplay {
    private String name;
    private AddressDisplay address;

    // Getters and Setters...
}
```

{% endtab %}
{% endtabs %}

The `ImplicitMappingTransformer` uses the ShapeShift instance internally to map `Address` to `AddressDisplay`.

## ImplicitCollectionMappingTransformer

`ImplicitCollectionMappingTransformer` has the same job as `ImplicitMappingTransformer` but for collections.

{% tabs %}
{% tab title="Kotlin" %}

```kotlin
@DefaultMappingTarget(UserDisplay::class)
class User {
    @MappedField
    var name: String? = null

    @MappedField(transformer = ImplicitCollectionMappingTransformer::class)
    var addresses: List<Address>? = null
}

class UserDisplay {
    var name: String? = null
    var addresses: List<AddressDisplay>? = null
}
```

{% endtab %}

{% tab title="Java" %}

```java
@DefaultMappingTarget(UserDisplay::class)
public class User {
    @MappedField
    private String name;

    @MappedField(transformer = ImplicitCollectionMappingTransformer.class)
    private List<Address> addresses;

    // Getters and Setters...
}

public class UserDisplay {
    private String name;
    private List<AddressDisplay> addresses;

    // Getters and Setters...
}
```

{% endtab %}
{% endtabs %}


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