Swift Combine: first() operator, return only a single value!
first() operator is mainly used for finding different values. As the name suggests, it’s going to find the first element in a sequence which matches the condition you defined. As soon as it finds that particular ‘true’ value, it’s going to stop for searching for the sequence.
Find a single value
let numbers = (1...9).publishernumbers
.first(where: { $0 % 2 == 0 }) // what you are looking for
.sink {
print($0) //2, nothing more will be printed than 2
}
I created a number sequence which is going from 1 to 9 and made it a publisher. first()
operator takes a closure where you should define a certain condition.
Note that it only returns a single value which met your condition.
You can think first() operator as a kind of lazy operator. When it finds the first condition that meets the criteria, then it simply bails out at that moment and give you that particular number from the sequence. So this is the usage of first() operator in the combine framework.
Conclusion
first()operator only returns a single value which meets your criteria.
