create objects/instances in variables swift

问题

I don't know how to use variables when creating Instances or adressing them in Swift: For exmaple how do I do following in a loop (creating Instances):

class Guest {
    let name: String
    var age: Int 
    init(name: String, age: Int) {
        self.name = name
        self.age = age
    }
}

let guests = [["ann", 1] , ["bob", 2] ...]

so that the loop equals :

let ann = Guest(name: "ann" , age: 1)
let bob = Guest(name: "bob" , age: 2)
...

edit: I am looking for something like this:

for i in guests {
  let i[0] = Guest(name: i[0] , age: i[1])

Example for adressing:

print(guests[0].age)
>>>1

I've searched a lot but am getting directed to issues regarding creating variables in classes.

Thank you very much!

回答1:

You can do that with a classic loop:

let input = [("Ann", 1), ("Bob", 2)]

var guests: [Guest] = []
for each in input {
    guests.append(Guest(name: each.0, age: each.1))
}

However, it can be done more concisely (and with avoidance of var) using functional techniques:

let guests = [("Ann", 1), ("Bob", 2)].map { Guest(name: $0.0, age: $0.1) }

EDIT: Dictionary-based solution (Swift 4; for Swift 3 version just use the classic loop)

let input = [("Ann", 1), ("Bob", 2)]
let guests = Dictionary(uniqueKeysWithValues: input.map {
    ($0.0, Guest(name: $0.0, age: $0.1))
})

Or, if it's possible for two guests to have the same name:

let guests = Dictionary(input.map { ($0.0, Guest(name: $0.0, age: $0.1)) }) { first, second in
    // put code here to choose which of two conflicting guests to return
    return first
}

With the dictionary, you can just do:

if let annsAge = guests["Ann"]?.age {
    // do something with the value
}

回答2:

   //MARK: Call method to create multiple instances 

createInstance([("Ann", 1), ("Bob", 2)])

func createInstance(_ input: Array<Guest>) {        
    for each in input {
        guests.append(Guest(name: each.0, age: each.1))
    }
}

来源：https://stackoverflow.com/questions/45989491/create-objects-instances-in-variables-swift

标签

swift

class

loops

variables