Swift iOS中Optional<NSMutableArray>无下标问题及数组转模型咨询

Hey there! Let's fix your two key issues step by step:

1. Fixing "value of type 'Optional' has no subscripts" Error #

The error pops up because dataArray is an Optional type (Optional<NSMutableArray>), and Swift blocks direct subscript access on optional values until you unwrap them. You need to safely unwrap the optional before accessing its elements.

Safe Unwrapping Options: #

Option 1: Using if let (for in-line processing)

// Safely unwrap the optional array
if let unwrappedDataArray = dataArray {
    // Now you can access elements with subscripts
    let firstElement = unwrappedDataArray[0]
    
    // Cast to Swift's native array type for easier handling (if it contains dictionaries)
    if let swiftArray = unwrappedDataArray as? [[String: Any]] {
        // Process the Swift array here
    }
} else {
    // Handle empty/nil array case
    print("dataArray is nil - no data to process")
}

Option 2: Using guard let (for early exit)

guard let unwrappedDataArray = dataArray else {
    print("dataArray is nil, exiting early")
    return
}

// Use the unwrapped array safely below
let firstItem = unwrappedDataArray[0]

2. Parsing responseStr into [ShakeInfo] Array #

The cleanest way to convert a JSON string to your ShakeInfo model array is using Swift's built-in Codable protocol. Here's how to implement it:

Step 1: Update Your ShakeInfo Model to Conform to Codable #

Make your model class adopt Codable (it works seamlessly with NSObject subclasses):

import Foundation

class ShakeInfo: NSObject, Codable {
    // Match these properties to your JSON keys exactly (use CodingKeys if names differ)
    var date: String?
    var shakeState: String? // Adjust type to match your actual data (e.g., Bool, Int)
    
    // Optional: Use CodingKeys if JSON uses different key names (e.g., snake_case)
    enum CodingKeys: String, CodingKey {
        case date
        case shakeState = "shake_state" // Example mapping for snake_case JSON
    }
    
    override init() {
        super.init()
    }
}

Step 2: Decode the JSON String to [ShakeInfo] #

Convert the string to Data, then use JSONDecoder to parse it into your model array:

// Convert response string to Data first
guard let jsonData = responseStr.data(using: .utf8) else {
    print("Failed to convert response string to Data")
    return
}

do {
    // Decode the Data into an array of ShakeInfo objects
    let shakeInfoDetails = try JSONDecoder().decode([ShakeInfo].self, from: jsonData)
    
    // Now you can use shakeInfoDetails as your model array!
    print("Successfully parsed \(shakeInfoDetails.count) ShakeInfo items")
} catch {
    // Handle decoding errors (print full error for debugging)
    print("Decoding failed: \(error.localizedDescription)")
    print("Full error details: \(error)")
}

Alternative: Manual Conversion (No Codable Needed) #

If you prefer manual parsing (e.g., if dataArray contains Objective-C dictionaries), loop through the unwrapped array and map each element to ShakeInfo:

if let unwrappedDataArray = dataArray as? [[String: Any]] {
    var shakeInfoDetails: [ShakeInfo] = []
    
    for itemDict in unwrappedDataArray {
        let shakeInfo = ShakeInfo()
        shakeInfo.date = itemDict["date"] as? String
        shakeInfo.shakeState = itemDict["shakeState"] as? String
        // Adjust type casting based on your actual data type (e.g., as? Bool)
        
        shakeInfoDetails.append(shakeInfo)
    }
    
    // shakeInfoDetails now contains your converted objects
}

内容的提问来源于stack exchange，提问作者Anand Gautam