Swift Collectionview Sections from a single array

Question

I have an array of IDs ["one", "two", "three"...]

These Ids are matched against a json I get from a URLSession and then displayed in a collectionview. At the moment it's just one simple collectionView with the feature to reorder it by long press and drag. But I need the possibilty to split it up in sections.

The best thing would be to make the sections dynamic, so that I can add as many sections as I want and then sort the cells into the sections. I get what I could do if I had an array for every section like

section1 = ["one", "two"]

section2 = ["three", "four"]

But I have no Idea how to realize this in my current setup.

Have a look at this tutorial on UICollectionView's by Raywenderlich. — David Pasztor
– David Pasztor, Commented Sep 5, 2017 at 9:02
This tutorial doesnt help very much. I'm familiar with a CollectionView but there are no sections added or data splitted up — theslash
– theslash, Commented Sep 5, 2017 at 9:11
myArray = [["one", "two", "three", "four"]] (one section). At some point myArray = [["one", "two"], [ "three", "four"]]. You retrieve cellForRowAt: myObject = myArray[indexPath.section][indexPath.row]. numberOfSection: myArray.count. numberOfItemsInSections: myArray[section].count, in pseudo code. — Larme
– Larme, Commented Sep 5, 2017 at 9:19

Jeffery Thomas · Accepted Answer · 2017-09-05 09:28:46Z

2

Don't do it. I'm sure you could figure out a way to keep the single array, but don't. The maintenance nightmare will haunt you.

Create a view of the data which is broken into an array of arrays.

struct MySection {
    let sectionId: String // or whatever section metadata you need.
    let data: [Data] // or whatever your real type is.
}

In the collection view controller

var dataView: [MySection]

All the data in 1 section

self.dataView = [MySection(sectionId: "all data", data: self.data)]

Grouping the data into different sections

self.dataView = self.data.reduce([]) { dataView, datum in
    var dataView = dataView // make a mutable data view

    let sectionId = self.determineSectionIdFromDatum(datum) // <-- slotting into sections

    // Add into an existing section or into a new section
    if let index = dataView.index(where: { $0.sectionId == sectionId }) {
        let data = dataView[index].data + [datum]
        dataView[index] = MySection(sectionId: sectionId, data: data)
    } else {
        let data = [datum]
        dataView.append(MySection(sectionId: sectionId, data: data))
    }

    return dataView
}

At this point you will likely need to sort either the sections or the data within the sections.

answered Sep 5, 2017 at 9:28

Jeffery Thomas

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3 Comments

Shades Over a year ago

That reduce function is fancy. +1

theslash Over a year ago

@Jeffery Thomas thanks for your suggestion. I think I have a bit of reading to do until I fully understand everything ;-) First Problem I see is that my Array is at the moment stored in the UserDefaults, and this won't work with a Struct so I'll have to find a way around this

Jeffery Thomas Over a year ago

@theslash The type of self.data doesn't matter here. I used [Data] as a placeholder. It could be [String], [[AnyHashable: Any]], or whatever data type is returned by UserDefaults.

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