# Apply

Creates a new [`Option<T>`](https://github.com/gabrielschade/tango/tree/379cc4a38ae47796971eb875ec66e7dc053a9081/Types/Option/Introduction.html) whose value is the result of applying the given `applying` function to `Option<T>.Some` value when both `applying` and `option` are `IsSome`.

Otherwise returns an `Option<T>.None()`.

| Parameters                                                         | Returns          |
| ------------------------------------------------------------------ | ---------------- |
| <p>Option\<Func\<T, TResult>> applying</p><p>Option\<T> option</p> | Option\<TResult> |

## Usage

This function is usually used to modify an option value by using an option function.

It works like a `Map` function, but in this case both value and the function are option values.

It's possible to use `Apply` function with two different syntaxes.

1. `Apply<T, TResult>(function)`: in this case the `function` can be a regular function;
2. `Apply(optionFunction)`: in this case the `function` needs to be a option function.

&#x20;**Expliciting an optional function**&#x20;

```csharp
Func<int, int> multiply2 = value => value * 2;
Option<Func<int, int>> optionFunction = multiply2;

Option<int> optionValue = 4;
Option<int> result = optionValue.Apply(optionFunction);

//result.IsSome = true
//result.Some = 8
```

&#x20;**Using a regular function**&#x20;

```csharp
Func<int, int> multiply2 = value => value * 2;

Option<int> optionValue = 4;
Option<int> result = optionValue.Apply<int,int>(multiply2);

//result.IsSome = true
//result.Some = 8
```

&#x20;**When the option function IsNone**&#x20;

```csharp
Option<Func<int, int>> optionFunction = 
    Option<Func<int, int>>.None();

Option<int> optionValue = 4;
Option<int> result = optionValue.Apply(optionFunction);

//result.IsSome = false
//result.IsNone = true
```

&#x20;**When the option value IsNone**&#x20;

```csharp
Func<int, int> multiply2 = value => value * 2;

Option<int> optionValue = Option<int>.None();
Option<int> result = optionValue.Apply<int,int>(multiply2);

//result.IsSome = false
//result.IsNone = true
```


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