如何使用Swift在Realm中保存多维数组并支持增删操作

Hey there! Sorry you’ve been stuck on this for a week—let’s break this down simply. Realm doesn’t support storing multidimensional arrays directly, but we can work around this by wrapping each sub-array in a Realm object. Here’s a step-by-step solution:

1. Define Realm Object Classes #

First, we’ll create two Realm Object subclasses: one to represent each sub-array, and another to hold the entire sequence of sub-arrays.

import RealmSwift

// This class wraps a single sub-array (e.g., [0, 1] or [0, 2, 1])
class SubSequence: Object {
    // Store the elements of the sub-array in a Realm List
    let elements = List<Int>()
    
    // Convenience initializer to convert a regular [Int] to a SubSequence
    convenience init(from array: [Int]) {
        self.init()
        elements.append(objectsIn: array)
    }
}

// This class holds the entire sequence of sub-arrays
class SequenceContainer: Object {
    // Store all SubSequence objects in a Realm List
    let sequences = List<SubSequence>()
    
    // Optional: Add an ID if you need to reference this container later
    @Persisted(primaryKey: true) var id: UUID = UUID()
    
    // Convenience initializer to convert your initial [[Int]] array
    convenience init(from sequenceArray: [[Int]]) {
        self.init()
        sequenceArray.forEach { subArray in
            sequences.append(SubSequence(from: subArray))
        }
    }
}

2. Save Your Initial Sequence to Realm #

Now you can take your existing [[Int]] array and save it to Realm using the container class:

let realm = try! Realm()

// Your initial sequence
let initialSequence = [[0, 1], [0, 2, 1], [4, 5, 1]]

// Create a container and save it to Realm
try! realm.write {
    let container = SequenceContainer(from: initialSequence)
    realm.add(container)
}

3. Add a New Sub-Array #

To add a new sub-array to your stored sequence, fetch the container and append a new SubSequence object:

// Fetch the container (assuming you're using the ID to find it)
guard let container = realm.objects(SequenceContainer.self).first else {
    print("No sequence container found!")
    return
}

// New sub-array to add
let newSubArray = [3, 0, 2]

try! realm.write {
    container.sequences.append(SubSequence(from: newSubArray))
}

4. Delete a Sub-Array #

To remove a sub-array, you can target it by index or by its contents:

Delete by Index #

try! realm.write {
    // Delete the 2nd sub-array (index 1, since arrays are 0-indexed)
    container.sequences.remove(at: 1)
}

Delete by Contents #

If you want to delete a sub-array that matches a specific [Int] value:

let targetSubArray = [0, 1]

// Find the SubSequence that matches the target array
if let targetSequence = container.sequences.first(where: {
    $0.elements.map { $0 } == targetSubArray
}) {
    try! realm.write {
        container.sequences.remove(object: targetSequence)
    }
}

5. Modify Elements in a Sub-Array #

You can also update individual elements within a sub-array:

// Get the first sub-array
guard let firstSubSequence = container.sequences.first else { return }

try! realm.write {
    // Change the first element from 0 to 9
    firstSubSequence.elements[0] = 9
}

Key Notes #

• Realm works best with object-oriented structures, so wrapping sub-arrays in SubSequence objects lets us leverage Realm’s built-in support for List collections.
• Always make sure to perform write operations inside a realm.write block—this ensures changes are persisted safely.

内容的提问来源于stack exchange，提问作者Dav Irv