Mapping two arrays two one object in swift

Question

I have two different arrays which am trying to map them to one object, using the information in the first array ModelOne id. I use two for loops to check if the id in model one appears in the second array if true create an object with model one id, name and array of all names in model two. From my implementation am not able to get the correct results.

// Model One struct ModelOne: Codable { let id: Int let name: String } // Model two struct ModelTwo: Codable { let id: Int let modelOneId: Int let name: String } var arrayOne = [ModelOne]() arrayOne.append(ModelOne(id: 1, name: "One")) arrayOne.append(ModelOne(id: 2, name: "Two")) var arrayTwo = [ModelTwo]() arrayTwo.append(ModelTwo(id: 1, modelOneId: 1, name: "Some name")) arrayTwo.append(ModelTwo(id: 2, modelOneId: 1, name: "Other name")) arrayTwo.append(ModelTwo(id: 1, modelOneId: 2, name: "Name one")) arrayTwo.append(ModelTwo(id: 2, modelOneId: 2, name: "Name two")) struct MappedModel { let id: Int let name: String let items: [String] } var arrayThree = [MappedModel]() for i in arrayOne { for x in arrayTwo { if i.id == x.id { arrayThree.append(MappedModel(id: i.id, name: i.name, items: [x.name])) } } }

jnpdx · Accepted Answer · 2021-07-28 22:58:10Z

3

If I'm interpreting the issue correctly, you want the MappedModel to have the id and name from ModelOne, with items containing all of the names from the ModelTwo where modelOneId matches the ModelOne id.

If so, this would do the trick:

var combined = arrayOne.map { item1 in MappedModel(id: item1.id, name: item1.name, items: arrayTwo.compactMap { $0.id == item1.id ? $0.name : nil}) }

Which yields:

[ MappedModel(id: 1, name: "One", items: ["Some name", "Other name"]), MappedModel(id: 2, name: "Two", items: ["Name one", "Name two"]) ]

edited Jul 28, 2021 at 22:58

answered Jul 28, 2021 at 22:50

jnpdx

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6 Comments

Leo Dabus Over a year ago

or using compactMap to avoid iterating the collection twice items: arrayTwo.compactMap { $0.id == item1.id ? $0.name : nil }

Leo Dabus Over a year ago

Note that OP is not using modelOneId if i.id == x.id { but not sure if that's what he needs

jnpdx Over a year ago

@LeoDabus I did note that. I'm making an assumption (that may be incorrect) that this is one of their issues, based on the naming scheme.

Leo Dabus Over a year ago

Yes I did notice that as well

jnpdx Over a year ago

@LeoDabus good idea with the compactMap -- adjusted. @Mzalendo see the revision history to see the original, which may be slightly more readable.

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