# Persistent variables source > Supply named variables to a Smart String through groups of serialized assets, without passing arguments. Supply named variables to a Smart String through groups of serialized assets, without passing arguments. The Persistent variables source lets you reference named values inside a placeholder instead of passing them as arguments to [`Smart.Format`](/engine/6000.7/script-reference/unity/smartstrings/smart/format.md). Values live in a [`VariablesGroupAsset`](/engine/6000.7/script-reference/unity/smartstrings/persistentvariables/variablesgroupasset.md), a [ScriptableObject](https://docs.unity3d.com/ScriptReference/ScriptableObject.html) that holds named variables. You register one or more groups with the source, each under a unique name, and reach a variable with dot notation: ```text {group-name.variable-name} {group-name.nested-group-name.variable-name} ``` ## Variables group asset A `VariablesGroupAsset` contains multiple persistent variables and nested groups. Create one from the Assets menu: **Assets > Create > Smart Strings > Variables Group**. Add variables in script with the `Add` method. Register the source with `Smart.Default.AddExtensions(...)` or on a specific [`SmartFormatter`](/engine/6000.7/script-reference/unity/smartstrings/smartformatter.md). The source first checks the current value for a matching variable group, then any group registered on the source. The value a variable returns is handled by the remaining sources and formatters, so you can apply formatters such as [Choose](/engine/6000.7/manual/scripting/smart-strings/formatters/choose-formatter.md) to it. The following example shows how to create and use named persistent variables: ```cs var group = ScriptableObject.CreateInstance(); group.Add("my-float", new FloatVariable { Value = 1.23f }); group.Add("my-string", new StringVariable { Value = "This is an example" }); group.Add("my-bool", new BoolVariable { Value = true }); var source = new PersistentVariablesSource(); source.Add("global", group); var smart = Smart.CreateDefaultSmartFormat(); smart.AddExtensions(source); // "My float value is 1.23" smart.Format("My float value is {global.my-float}", null); ``` Group names and variable names must be unique and must not contain whitespace; any whitespace is replaced with `-` when a name is added. | Smart String | Result | | -------------------------------------------------------------------------- | -------------------------------------- | | `My float value is {global.my-float}` | My float value is 1.23 | | `{global.my-string} of using variables.` | This is an example of using variables. | | `The door is {global.my-bool:Open\|Closed}.` | The door is Open. | | `This is an integer {global.int-variable} as hex {global.int-variable:X}.` | This is an integer 255 as hex FF. | | `Values can be nested {global.nested-group.player-name}` | Values can be nested Player 1 | ## Variable types The following variable types are available by default. Each holds a single value of its type: | Type | Description | | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | -------------------------------------------------------------------------------------------- | | [`BoolVariable`](/engine/6000.7/script-reference/unity/smartstrings/persistentvariables/boolvariable.md) | A single `bool` value. | | [`SByteVariable`](/engine/6000.7/script-reference/unity/smartstrings/persistentvariables/sbytevariable.md), [`ByteVariable`](/engine/6000.7/script-reference/unity/smartstrings/persistentvariables/bytevariable.md) | A single signed or unsigned byte value. | | [`ShortVariable`](/engine/6000.7/script-reference/unity/smartstrings/persistentvariables/shortvariable.md), [`UShortVariable`](/engine/6000.7/script-reference/unity/smartstrings/persistentvariables/ushortvariable.md) | A single signed or unsigned short value. | | [`IntVariable`](/engine/6000.7/script-reference/unity/smartstrings/persistentvariables/intvariable.md), [`UIntVariable`](/engine/6000.7/script-reference/unity/smartstrings/persistentvariables/uintvariable.md) | A single signed or unsigned int value. | | [`LongVariable`](/engine/6000.7/script-reference/unity/smartstrings/persistentvariables/longvariable.md), [`ULongVariable`](/engine/6000.7/script-reference/unity/smartstrings/persistentvariables/ulongvariable.md) | A single signed or unsigned long value. | | [`FloatVariable`](/engine/6000.7/script-reference/unity/smartstrings/persistentvariables/floatvariable.md), [`DoubleVariable`](/engine/6000.7/script-reference/unity/smartstrings/persistentvariables/doublevariable.md) | A single float or double value. | | [`StringVariable`](/engine/6000.7/script-reference/unity/smartstrings/persistentvariables/stringvariable.md) | A single `string` value. | | [`ObjectVariable`](/engine/6000.7/script-reference/unity/smartstrings/persistentvariables/objectvariable.md) | A reference to a UnityEngine [Object](https://docs.unity3d.com/ScriptReference/Object.html). | | [`NestedVariablesGroup`](/engine/6000.7/script-reference/unity/smartstrings/persistentvariables/nestedvariablesgroup.md) | A reference to another `VariablesGroupAsset`, which allows variables to nest. | ## Triggering updates Each variable derives from [`Variable`](/engine/6000.7/script-reference/unity/smartstrings/persistentvariables/variable1.md) and raises a `ValueChanged` event when its `Value` changes. Variables that implement [`IVariableValueChanged`](/engine/6000.7/script-reference/unity/smartstrings/persistentvariables/ivariablevaluechanged.md) can drive automatic updates in callers that subscribe to that event. To change several variables and notify once at the end, wrap the changes in an update scope: ```cs using (PersistentVariablesSource.UpdateScope()) { floatVariable.Value = 2.5f; stringVariable.Value = "Updated"; } ``` ## Custom variables A custom variable must be `[Serializable]` and implement [`IVariable`](/engine/6000.7/script-reference/unity/smartstrings/persistentvariables/ivariable.md). Return the value from `GetSourceValue`, which other sources and formatters then process. Implement `IVariableValueChanged` to support automatic updates. ```cs [Serializable] public class DateTimeVariable : IVariable { public object GetSourceValue(ISelectorInfo selector) => DateTime.Now; } ``` ## Additional resources * [Create a custom source](/engine/6000.7/manual/scripting/smart-strings/sources/create-a-custom-source.md) * [Choose formatter](/engine/6000.7/manual/scripting/smart-strings/formatters/choose-formatter.md) * [Smart Strings](/engine/6000.7/manual/scripting/smart-strings.md)