试图快速声明自定义对象的数组

Question

Here is my code

    var planetNames = ["mercury", "venus", "earth", "mars", "jupiter", "saturn", "uranus", "neptune", "pluto"] //names of the planets

    for currentRing in 0..<orbitMarkers.count
    {
        var planetNames[currentRing] = planet(size: 1.2)

    }

and here is my class

class planet
{
   var size: CGFloat
   init(size: CGFloat)
   {
     self.size = size
   }
}

I am trying to figure out how I can make an array of 8 new "planet" objects

Answer 1

you can do it like this:

class planet
{
    var name: String
    var size: CGFloat
    init(name: String, size: CGFloat)
    {
        self.size = size
        self.name = name
    }
}

var planets: [planet] = []
var mercury = planet(name: "Mercury", size: 20)
planets.append(mercury)

I added a name variable for your planet class, and then the array initialization is var planets: [planet] and as an example I have appended one planet for you to see how its done.

Answer 2

It looks like you already have an array of orbit markers.. do you have an array of sizes?

Also, name your class with UpperCamelCase

class Planet {
    let name: String
    let size: CGFloat
}

let sizes: CGFloat = [1,2,3,....] // planet sizes
let names = ["mercury", "x", ...] // planet names

let planets = zip(names, sizes).map{Planet(name: $0, size: $1)}

Also.. size is a little bit nondescript. Consider changing it to radius, volume, diameter or whatever the value actually represents.

Quick explanation - zip combines two arrays of equal sizes into one array of tuples, attaching elements pairwise into a tuple. Element 1 from array 1 is paired with element 1 from array 2, etc.

Map performs an operation on every tuple in the array of tuples that resulted from the zipping, return a Planet object for each tuple.

Answer 3

Custom class array example swift 3.0

class Planet {
    var name: String!
    var size: CGFloat!

    init(name:String,size:CGFloat) {
        self.name = name
        self.size = size
    }
}

var planets = [Planet]()
let planet = Planet(name: "Earth", size: 1.2)
planets.append(planet)

for Planet in planets {
    print(Planet.name)
}

Answer 4

This is how you would do it in Swift 3

var planets = [planet]() // Initialize an array of type planet
var mercury = planet()   // Initialize an instance of type planet
mercury.size =           // set size on mercury
planets.append(mercury)  // Add mercury to the array planets

This is untested, but those are some basic statements working with an array of a custom type.

EDIT: I just noticed you have an initializer set up which means you could make a planet like this.

var earth = planet(size: earthSizeHere) // Use initializer
planets.append(earth)