Hi all, I’m fairly new to Kotlin. I’m trying to im...

# getting-started

[Pratik Khandelwal]

Hi all, I’m fairly new to Kotlin. I’m trying to implement the below code. The getCurrentSubscription method returns a `Subscription?nullable type. Doing a.let` makes the it also type of Subscription? . I though .let should pass on a non-null Subscription inside.

Now my cancelSubscription method expects a non-nullable it.id which is causing issues. What am I missing here?

getCurrentSubscription.invoke(customerId).let {
      cancelSubscription.invoke(it.id, cancelled).let { subscription ->
        subscriptionApiMapper.fromDomainModel(subscription)
      }
    }

[Rob Elliot]

Use getCurrentSubscription.invoke(customerId)?.let { (note the question mark) to have it be non-null.

[Rob Elliot]

let just passes the receiver to the lambda, so it can be used on nullable and non-nullable typed receivers. By doing a safe null-dereference (?.let) you tell the compiler that the receiver of let is definitely not null.