same value in dictionary in swift

Question

I m mapping data that come from service with using dictionary [String: String]. I collect them dictionary array. For example, if their parent ids are the same, I want to add their values by array value.

["ParentId": "1","Value": "["Giyim","Aksesuar","Ayakkabı"]"]

It is also the reason I don't know parent id sometimes on the left sometimes on the right in photo

Here is my code and its output.

struct Categories {

    let parentId: String
    let values: [String]

}

                for result in results {

                    if result?.parentCategoryId != "" {
                        
                        for docId in self.docIds {
                            
                            if result?.parentCategoryId == docId {
                                
                                //print(result?.name)
                                var values = [String]()
                                values.append(result?.name ?? "")
                                
                                self.newCat.append(Categories(parentId: docId, values: values))
                                
                            }
                        }
                        
                    }
                }

Answer 1

Problem

As far as I understand from the description you want to map some service data structure to a dictionary where key is parentId and value is an array of some items referred to parentId.

I believe your problem comes from a misunderstanding of the concept of dictionary as a data structure. [String: String] is dictionary where keys and their associated values are of String type. For example:

["firstKey": "firsthValue", "secondKey": "secondValue", ...]

That means you cannot store associated values of String and Array types in the same dictionary , as you already told the compiler you would like to store only strings.

It is also the reason I don't know parent id sometimes on the left sometimes on the right in photo

This is because key-value pairs are stored in the dictionary without order. This is how dictionaries work:) I'd strongly recommend reading some short official materials to get used to them.

• New Swift 5.4 version has a new OrderedDictionary data structure, where keys are ordered, but there is absolutely 100500% no reason to use it for your problem*

Possible solutions

In your case i would suggest either use some struct:

struct SomeData {
    let parentID: Int
    var values: [String]
}

var storage: [SomeData] // alternative to emptyDic

// Filling storage with data from service
for result in inputData {
    // search for SomeData with required id, add value
    // OR create SomeData if there is no such id in array yet
}

OR [personally this appeals to me more]

Store data in [String: [String]] dictionary, where the key is parentID and the associated value is an array of values. The algorithm of filling this dictionary is pretty the same:

1. You add new key-value pair for every new parentID
2. You append new values for parentIDs that are already in the dictionary.

Answer 2

Using the struct approach, you could do something like this (you'll need to adapt it to your code, but that should be straightforward):

struct Categories {
    let parentId: String
    var values: [String] //notice this needs to be a var, not a let
}

func addItem(categories : inout [Categories], docId: String, name: String) {
        if let index = categories.firstIndex(where: { $0.parentId == docId }) {
            categories[index].values.append(name)
        } else {
            categories.append(Categories(parentId: docId, values: [name]))
        }
}

func addValues() {
  var categories = [Categories]()
  addItem(categories: &categories, docId: "4", name: "Test1")
  addItem(categories: &categories, docId: "1", name: "Test")
  addItem(categories: &categories, docId: "4", name: "Test2")
  addItem(categories: &categories, docId: "4", name: "Test3")
  print(categories)

  //in your code, it'll look more like:
  // addItem(categories: &self.newCat, docId: docId, name: result?.name ?? "")
} 

Which yields this:

[
  StackOverflowPlayground.Categories(parentId: "4", values: ["Test1", "Test2", "Test3"]), 
  StackOverflowPlayground.Categories(parentId: "1", values: ["Test"])
]

I still wonder whether you maybe just want a Dictionary that is keyed by the parentId , but not knowing your use case, it's hard to say.