How do I append one `Dictionary` to another `Dictionary` using Swift?

I am using the `AlamoFire` library to send JSON content to a [REST](https://en.wikipedia.org/wiki/Representational_state_transfer) server.

**Dictionary 1**

```
var dict1: [String: AnyObject] = [
    kFacebook: [
        kToken: token
    ]
]

```

**Dictionary 2**

```
var dict2: [String: AnyObject] = [
    kRequest: [
        kTargetUserId: userId
    ]
]

```

How do I combine the two dictionaries to make a new dictionary as shown below?

```
let parameters: [String: AnyObject] = [
    kFacebook: [
        kToken: token
    ],
    kRequest: [
        kTargetUserId: userId
    ]
]

```

I have tried `dict1 += dict2`, but I got a compile error:

> 
> Binary operator '+=' cannot be applied to two '[String : AnyObject]' operands
> 
> 
>