Why are MutableLiveData variables declared with equals sign (=)?

Question

In Kotlin, when declaring the type of variable, a colon is used. Even when declaring LiveData, a colon is used. So why is an equals sign used for MutableLiveData? I haven't been able to figure this out. I spent about 2 hours a few days ago trying to understand why my MutableLiveData variable wasn't working only to realize I needed an equals instead of a colon.

Example:

private val _liveData = MutableLiveData<Int>()  
val liveData: LiveData<Int>

Thanks in advance!

Answer 1

Kotlin auto detects the type, so you do not need to specify it. These are equivalent

val foo: Int = 123
val foo = 123

However, if you have a variable that is initialized later, you must provide the type, as otherwise the compiler can't determine what type it is. For instance,

class MyClass {
    val foo: Int  // must specify type

    init {
        foo = /* compute foo */
    }
}

It has nothing to do with LiveData or MutableLiveData.