I have a Class like this:

```
class TestClass {
    let str = "string"
}

```

Now, I know two ways to create an instance.

First way:

```
let firstTestInstance: TestClass!
firstTestInstance = TestClass()

```

Second way:

```
let secondTestInstance = TestClass()

```

I want to know:

* What is the difference between the first way and the second way?
* Which is better? Why?
* Are there are other ways to create Instance?

PS: I saw the Swift Document use second way.