How to add value from object in dictionary in Swift? - swift

Question

I have dictionary which is having objects as value, I want to retrieve value from object.
code :
public class Student {
public let name: String
public let age: Double
public init(name: String, age: Double) {
self.name = name
self.age = age
}
}
and dictionary as ["1": Student, "2" : Student ]
How can i add all the ages of student? for 13 + 12.

Answer 1

Here are potential solutions:
let dict = ["1": Student(name: "A", age: 13), "2" : Student(name: "B", age: 12)]
Side note, there is nothing wrong in doing a manual for loop. It's basic algorithm skills, and it's need to understand higher level methods.
Basic for loop:
var sumOfAges: Double = 0
for (_, value) in dict {
sumOfAges += value.age
}
print(sumOfAges)
Basic forEach loop
var sumOfAges2: Double = 0
dict.forEach {
sumOfAges2 += $0.value.age
}
With reduce(into:_:):
let sumOfAges3: Double = dict.reduce(into: 0) { partialResult, aKeyValue in
partialResult += aKeyValue.value.age
}
With reduce(into:_:), and using Shorthand Argument Names (which make sense only if you understand the previous step):
let sumOfAges4 = dict.reduce(into: 0, { $0 += $1.value.age })
Side note, since the output is just a number, reduce(_:_:) is enough:
let sumOfAges5 = dict.reduce(0) { $0 + $1.value.age })
Additional possible step, is to transform your dictionary into a simpler data, like an array of Double.
let allAges = dict.mapValues { $0.age }
// or let allAges = dict.mapValues { \.age }
// or let allAges = dict.values.map { $0.age }
// or let allAges = dict.values.map { \.age }
// ...
You have an array of Double, then, use either a for loop, forEach, reduce(into:_) again on this "simplified array"
The downside, is that you iterate twice, one for the mapping, one for your calculation.
Edit: Added commented alternative solutions by #Leo Dabus