# Types

### Simple Types

The[ Linx plugin](/reference/plugins/linx.md) contains all Simple Types. These include:

* [Boolean](/reference/plugins/linx/content/boolean.md)
* [Byte](/reference/plugins/linx/content/byte.md)
* [DateTime](/reference/plugins/linx/content/datetime.md)
* [Decimal](/reference/plugins/linx/content/decimal.md)
* [Double](/reference/plugins/linx/content/double.md)
* [Integer](/reference/plugins/linx/content/integer.md)
* [String](/reference/plugins/linx/content/string.md)

Use a Simple Type to create a variable in a Function by:

1. Dragging the type from the plugins panel onto the body of a Function.
2. Setting the *Value* property.

![Using Simple Types](/files/hX2fAIw2VTv56jlbfnXp)

***

### Complex Types

In the Linx Designer, Complex Types are just referred to as *Types*.

A *Type* in Linx works just like a JSON object. *Types* contain collections of named properties. Each property represents a *Simple Type*, a complex *Type*, or a *List*.

**Creating a Complex Type**

1. Click the *Type* button in the toolbar to add a type to your solution.
2. Set a name for the *Type* in the Properties panel.
3. Add properties to the *Type* using the *Type Editor*:
   * Add a name for each property in the *Name* column.
   * Select the property type in the *Type* column dropdown.

![Using Complex Types](/files/IBwV4WIxOd6s4PSpMSLw)

This example shows a \*Type\* with four properties (Address is of type 'Type\_Address', Children is a List of type 'Type\_Child', DOB is of type DateTime, and Name is of type String)

Here is a JSON representation of the Type\_Person type:

{% code overflow="wrap" %}

```json
{ "Person": { "Address": { "Street": "", "City": "", "POCode": "" }, "Children": [], "DOB": "", "Name": "" } }
```

{% endcode %}

## Using a Complex Type

1. Drag the Type from the Solution Explorer onto the Function body.
2. By default, the type is instantiated as empty using squiggly brackets `{}`, but its properties are not initialized and default to null.

![Instantiated, empty type](/files/APiZSflq4pkq0CHWpRxa)

3. Set values for Type properties by either:
   * Launching the Values Editor to add values.

![Drag the type into the Function](/files/DaZophGhpTrAW0bP7EoI)

```
*   Using a[ SetValue](../reference/plugins/linx/content/setvalue.md) function.
```

<div align="left"><img src="/files/FNz7Lo7tlv0PRGRpYmOP" alt="Using a SetValue to set a Type property"></div>

***

### Lists

Lists can be of any simple or complex type.

#### Creating a List

1. Drag a [List](/reference/plugins/linx/content/genericlist.md) from the Linx plugin onto the Function body.
2. An empty List will be initialized using square brackets `[]`.
3. Choose the List type in the property dropdown (it defaults to String).

![Select a List type](/files/563zXuC87uu7zuY8gCHs)

#### Adding Items to Lists

Add items to Lists by either:

1. Launching the List editor.

![Using a List](/files/70MFZESCvrv1Yaif1L6O)

1. Dragging an[ AddToList](/reference/plugins/linx/content/addtolist.md) function into the Function.
2. Selecting the List and value to add in the AddToList properties.

![Adding to a List](/files/FosngjFN17MHdKDeqLC2)

Other functions to manipulate the list are available in the Linx plugin.

![List Functions](/files/Vy5sJFWM1MQlCRTqXWZw)

***

### Assignment Errors

A common problem is caused by the attempt to assign values to NULL elements.

1. To set a value for a property of a complex type, the type cannot be null.

   ![Attempting to set an uninstantiated type causes an 'Object reference not set to an instance of an object' error](/files/sN3Yu4WIrd2ihw9ko1Yx)
2. Instantiate a Complex type inside another one with `{"PropertyName":{}}`.

   <div align="left"><img src="/files/uBkjijqFMTA3LwZvSBuq" alt="Complex types that are properties of other complex types must be instantiated before they can be used"></div>
3. Lists must be instantiated before they can be added to.

   ![Attempting to add items to an uninstantiated List causes a 'Cannot add to list as it is null' error](/files/prVS9ZeX0HNPh6sb0mDP)
4. Instantiate Lists that are properties of complex types with `{"PropertyName":[]}`.

   <div align="left"><img src="/files/rLnS3btbGfFFQ8EUQu5j" alt="Lists that are properties of complex types must be instantiated before they can be used"></div>

***

### Tutorial Video

{% embed url="<https://youtu.be/LwHlp1UAwOk>" %}


---

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