Get list of unique records based on specific key, value pair-CodePudding

I am new to swift and i was wondering if i could get unique values based on the key, value pair from 2 arrays.

Array-1 :

let arr1 = [
   ["title" : "News", "icon" : "news_1"],
   ["title" : "Food", "icon" : "food_1"]
]

Array-2 :

let arr2 = [
   ["title" : "News", "icon" : "news_2"],
   ["title" : "Technology", "icon" : "tech_1"]
]

How to get a result something like

Array-3 :

let arr3 = [
   ["title" : "Food", "icon" : "food_1"],
   ["title" : "Technology", "icon" : "tech_1"]
]

So I need the set of all unique values from array-1 and array-2 based on key named "title" in a resulting array.

Note : Here i have title "food" in array-1 and 2 but the icon is different.

CodePudding user response：

What you are looking for is probably the symmetric difference for those two arrays. But as pointed out in the comments, your data structure is not well suited for this. If you really want to stick to this current structure, this might work for you:

func symmetricDifference(arrays: [[[String: String]]], by key: String) -> [[String: String]] {
    var result = [String: [String: String]?]()
    for array in arrays {
        for element in array {
            guard let keyValue = element[key] else {
                // Ignore elements that do not contain the key, adjust as needed
                continue
            }
            
            // Check if we already saw the value
            if result[keyValue] == nil {
                // Add the element
                result[keyValue] = element
            } else {
                // We saw this keyValue already, remove the element
                result.removeValue(forKey: keyValue)
            }
        }
    }
    
    // Only return non nil elements
    return result.values.compactMap { $0 }
}

// Usage
symmetricDifference(arrays: [arr1, arr2], by: "title")

By using a better suited data structure, you could easily use the built-in Set operator:

struct Category: Hashable {
    let title: String
    let icon: String
    
    func hash(into hasher: inout Hasher) {
        hasher.combine(title)
    }
    
    static func ==(lhs: Category, rhs: Category) -> Bool {
        lhs.title == rhs.title
    }
}

let set1 = Set([Category(title: "News", icon: "news_1"), Category(title: "Food", icon: "food_1")])
let set2 = Set([Category(title: "News", icon: "news_2"), Category(title: "Technology", icon: "tech_1"), Category(title: "News", icon: "news_2")])
let result = set1.symmetricDifference(set2)