Reactive Programming in iOS with Combine

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Okay, that was a lot of information about transforming operators, so I've got a challenge for you before moving on. For this challenge, you need to create a publisher that does two things. Receive a string of 10 numbers or letters, look up those numbers in a context data structure. The starter plate ground, and the challenge folder for this part of the course has a context dictionary and three functions to help you out. You'll need to create a subscriber to the provided and per publisher and use the functions and transforming operators to do the following. Convert the input to numbers. Make sure you handle nil cases where the string can't be converted to numbers. If you get a nil from the conversion, replace it with zero collect 10 values at a time and format the collected strings to match the three digit area code and seven digit phone number format used in the United States. Dial the input received from the previous operator using the dial function. And don't forget closures and functions can be passed into operators, as long as their function signatures match up. Pause the video, try the challenge and then come back to see the solution. (upbeat music) Do you get the expected results? Let's break down the subs we went over earlier with some actual code. First, you need to convert the input string one character at a time using the convert method, which can be done with the map operator. Then replace any nils with zeros. We wanna form a 10 digit phone number with the values from the previous operations. So we need to collect 10 of them together to get a phone number. We can do that with the collect operator and once that's done, we can map those results to a nicer looking format with the format function. Finally, we can walk through each phone number and dial it using the dial function passed into the map operator and pass that end result into a sync subscriber that prints out the result.