Swift 3 ObjectOriented Programming - Second Edition

Chaining filter, map, and reduce

We can chain filter, map, and reduce. The following lines declare a new summedHighestScoresWhere method for our previously coded GameRepository class that chains filter, map, and reduce calls. The code file for the sample is included in the swift_3_oop_chapter_07_30 folder:

    open func summedHighestScoresWhere(minPlayedCount: Int) -> Int { 
      return getAll().filter({ $0.playedCount >= 
      minPlayedCount }).map({ $0.highestScore }).reduce(0) { 
        sum, highestScore in 
        return sum + highestScore 
      } 
    } 

The summedHighestScoresWhere method receives a minPlayedCount argument of the Int type and returns an Int value. The code calls the getAll and filter methods to generate a new Array<Game> with only the Game instances, whose playedCount ...