Yes when you write
if let a = optA, let b = optB, let c = optC {
}
Swift does execute the body of the IF only if all the optional bindings are properly completed.
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Another feature of this technique: the assignments are done in order.
So only if a value is properly assigned to a, Swift tries to assign a value to b. And so on.
This allows you to use the previous defined variable/constant like this
if let a = optA, let b = a.optB {
}
In this case (in second assignment) we are safely using a because we know that if that code is executed, then a has been populated with a valid value.