How to create an array of dictionaries? - arrays

Question

new to programming!
I'm trying to create an array of dictionaries inside a struct in Swift like so:
var dictionaryA = [
"a": "1",
"b": "2",
"c": "3",
]
var dictionaryB = [
"a": "4",
"b": "5",
"c": "6",
]
var myArray = [[ : ]]
myArray.append(dictionaryA)
myArray.append(dictionaryB)
This works fine in a playground, but when I put it into an Xcode project, inside a struct, the lines with the append function produce the error "Expected declaration".
I've also tried using the += operator with the same result.
How can I successfully construct this array inside the struct?

Answer 1

From your error Expected declaration, I assume you are doing like:
struct Foo {
var dictionaryA = [
"a": "1",
"b": "2",
"c": "3",
]
var dictionaryB = [
"a": "4",
"b": "5",
"c": "6",
]
var myArray = [[ : ]]
myArray.append(dictionaryA) // < [!] Expected declaration
myArray.append(dictionaryB)
}
This is because you can place only "declarations" in the struct body, and myArray.append(dictionaryA) is not a declaration.
You should do that somewhere else, for example in the initializer. The following code compiles.
struct Foo {
var dictionaryA = [
"a": "1",
"b": "2",
"c": "3",
]
var dictionaryB = [
"a": "4",
"b": "5",
"c": "6",
]
var myArray = [[ : ]]
init() {
myArray.append(dictionaryA)
myArray.append(dictionaryB)
}
}
But as #AirspeedVelocity mentioned, you should provides more information about myArray, or myArray would be Array<NSDictionary> which I think you don't expect.
Anyway, the correct solution would vary depending on what you really trying to do:
Maybe or maybe not, what you want is something like:
struct Foo {
static var dictionaryA = [
"a": "1",
"b": "2",
"c": "3",
]
static var dictionaryB = [
"a": "4",
"b": "5",
"c": "6",
]
var myArray = [dictionaryA, dictionaryB]
}
But, I don't know, why don't you just:
struct Foo {
var myArray = [
[
"a": "1",
"b": "2",
"c": "3",
],
[
"a": "4",
"b": "5",
"c": "6",
]
]
}

Answer 2

The problem lies with this line:
var myArray = [[ : ]]
You need to tell Swift what type myArray is – [[:]] isn’t enough information.
You can either do it the explicit way:
var myArray: [[String:String]] = [[ : ]]
Or, if practical, implicitly using the first or both values you plan to put in:
var myArray = [dictionaryA]
var myArray = [dictionaryA,dictionaryB]
(as an alternative to the explicit empty version, you can also write var myArray = [[String:String]](), which is shorthand for var myArray = Array<Dictionary<String,String>>())

Answer 3

var arrayOfDict = [[String: Int]]()
// Create a dictionary and add it to the array.
var dict1: [String: Int] = ["age": 20]
arrayOfDict.append(dict1)
// Create another dictionary.
var dict2: [String: Int] = ["rank": 5].
arrayOfDict.append(dict2)
// Get value from dictionary in array element 0.
if let value = arrayOfDict[0]["age"] {
print(value)
}
Output
20

Answer 4

Or you can use an array of tuples that´s even easier, like this:
var myArray:[(a:String,b:String,c:String)] = []
And append any element you need later:
self.myArray.append((a:"A",b:"B",c:"c"))
And to use them just:
self.myArray[index].a
self.myArray[index].b
self.myArray[index].c