So far, we have learned about different functions and seen some examples of them. Let's see if we can combine them to solve problems that we may encounter in our day-to-day application development.

Let's assume that we need to receive an object from a backend system as follows:

struct User { 
    let name: String 
    let age: Int 
} 

let users = [ 
    User(name: "Fehiman",  age: 60), 
    User(name: "Neco",  age: 29), 
    User(name: "Grace",  age: 1), 
    User(name: "Tamina",   age: 6), 
    User(name: "Negar", age: 27) 
] 

Then we need to calculate the total of ages by using totalAge in the users array. We can use a combination of the map and reduce functions to calculate totalAge as follows:

let totalAge = users.map { $0.age }.reduce(0) { $0 + $1 } 

We were able to chain the map and reduce methods to achieve this.