Swift 作为字典值的元组 Swift 5

Question

I have a Dictionary with a key of type String and values as a tuple:

var dictionaryTuple = [String: (x: Double, y: Double)]()

How do I set and access the values of the tuple. This is what I tried

dictionaryTuple["One"].x = 5.5 - compiler gives an error: Value of optional type '(x: Double, y: Double)?' must be unwrapped to refer to member 'x' of wrapped base type '(x: Double, y: Double)' see playground screenshot below Not sure why the compiler is giving an error. I have not declared the tuple as optional or the dictionary as an optional

When I change to: dictionaryTuple["One"]?.x = 5.5 - compiler is happy but I am not getting any value back

If I change it to: dictionaryTuple["One"]..x = 5.5 - it crashes.

What am I doing wrong? Do I need to initialize the tuple before using it? if so how?

Thanks very much!

Answer 1

Why not construct your struct like this?

struct DT {
    let key: String
    let x: Double
    let y: Double
}

let dt = DT(key: "One", x: 1, y: 2)

---

If you really want your own way, same as in your question:

struct DT {
    var dictionaryTuple = [String: (x: Double, y: Double)]()
}


var dt = DT(dictionaryTuple: ["One": (x: 1, y: 2)])

print(dt)//prints -> DT(dictionaryTuple: ["One": (x: 1.0, y: 2.0)])

var tuple: (x: Double, y: Double) = dt.dictionaryTuple["One"]!
tuple.x = 100
tuple.y = 200

//apply
dt.dictionaryTuple["One"] = tuple

print(dt)//prints -> DT(dictionaryTuple: ["One": (x: 100.0, y: 200.0)])

the key here is that I explicitly declary the type of the tuple variable, and cast it.

Answer 2

You can insert either a tuple like this

dictionaryTuple["One"] = (3.3, 4.4)

or update an existing one but then you need to treat it as an optional.

dictionaryTuple["Two"]?.x = 5.5

or supply a default value when updating.

dictionaryTuple["Three", default: (0.0, 0.0)].x = 5.5

Performing these 3 operations will mean the dictionary contains 2 tuples

var dictionaryTuple = [String: (x: Double, y: Double)]()
dictionaryTuple["One"] = (3.3, 4.4)
dictionaryTuple["Two"]?.x = 5.5
dictionaryTuple["Three", default: (0.0, 0.0)].x = 5.5
print(dictionaryTuple)

["Three": (x: 5.5, y: 0.0), "One": (x: 3.3, y: 4.4)]