SwiftUI Array List

Question

I've created a list of food products with stored data such as calories, protein, category, etc. I've made an array of categories in order to categorize these products into groups and I'm now trying to reference this array when stating the data in each product, but when doing this (Apple variable in line 16) I get the error:
"Cannot use instance member 'categories' within property initializer; property initializers run before 'self' is available"

This is my code:

struct Product : Identifiable {
    var id = UUID()
    var productName : String
    var calories : Double
    var protein : Double
    var carbs : Double
    var fats : Double
    var weight : Double
    var category : String
    
}

struct Data {
    @State var categories = ["Animal Products", "Dairy", "Fast Food", "Fruits", "Grains", "Nuts", "Vegetables", "Wheat"]
    
    var Apple = Product(productName: "Apple", calories: 52, protein: 0.3, carbs: 14, fats: 0.2, weight: 80, category: categories[3])
    var Avocado = Product(productName: "Avocado", calories: 160, protein: 2, carbs: 9, fats: 15, weight: 600, category: <#T##String#>)
    var Banana = Product(productName: "Banana", calories: 89, protein: 1.1, carbs: 23, fats: 0.3, weight: 120, category: <#T##String#>)
    var Broccoli = Product(productName: "Broccoli", calories: 34, protein: 2.8, carbs: 5, fats: 0.4, weight: 225, category: <#T##String#>)
    var Burger = Product(productName: "Burger", calories: 264, protein: 13, carbs: 30, fats: 10, weight: 110, category: <#T##String#>)
    var Carrot = Product(productName: "Carrot", calories: 41, protein: 0.9, carbs: 10, fats: 0.2, weight: 61, category: <#T##String#>)
    var Cheerios = Product(productName: "Cheerios", calories: 379, protein: 6, carbs: 83, fats: 5, weight: 40, category: <#T##String#>)
    var Cherry = Product(productName: "Cherry", calories: 50, protein: 1, carbs: 12, fats: 0.3, weight: 5, category: <#T##String#>)
}

How can I include this array inside of the Product list?

First it is Swift naming convention to name your properties starting with a lowercase letter. Second Swift already have a native structure called Data. You should name it something else to avoid ambiguity — Leo Dabus
– Leo Dabus, Commented Oct 13, 2020 at 22:00
There is many ways to fix your issue. The easiest one is to declare your variables as lazy — Leo Dabus
– Leo Dabus, Commented Oct 13, 2020 at 22:04

Asperi · Accepted Answer · 2020-10-14 05:09:23Z

1

It looks like categories are predefined, then here is a solution for your case - make categories static constant:

struct Data {
    static let categories = ["Animal Products", "Dairy", "Fast Food", "Fruits", "Grains", "Nuts", "Vegetables", "Wheat"]

    var Apple = Product(productName: "Apple", calories: 52, protein: 0.3, 
                  carbs: 14, fats: 0.2, weight: 80, category: categories[3])
   
    //  ... others
}

answered Oct 14, 2020 at 5:09

Asperi

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2 Comments

pawello2222 Over a year ago

Don't you need Self.categories[3]?

Asperi Over a year ago

@pawello2222, no, compiler understands the scope, at least Xcode 12 / swift 5.3.

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