使用PushPad的iOS App注册推送通知时崩溃求助（Xcode9/Swift4）

Hey there, let's break down why your app is crashing at that JSONDecoder line and fix it step by step.

First, Reveal the Exact Error #

The try? operator swallows errors and returns nil, which is why you're stuck with a vague crash instead of actionable details. Replace that guard block with a do-catch block to get concrete error information—this is the most critical first move:

case .Success(let data):
    do {
        let device = try JSONDecoder().decode(Device.self, from: data)
        completion(device.id, true)
    } catch {
        // Print the full error to pinpoint the issue
        print("Device decoding failed with error: \(error)")
        // Print the raw JSON string to compare against your model
        if let rawJson = String(data: data, encoding: .utf8) {
            print("Received raw JSON: \(rawJson)")
        }
        // Fallback to failure completion instead of crashing
        completion(nil, false)
    }

This will tell you exactly if the problem is a mismatched property name, incorrect data type, missing required field, or invalid JSON.

Common Causes & Fixes #

Once you have the error details, here are the most likely issues to address:

• Mismatched Model & JSON Structure
  Swift 4's Codable requires exact matches between your Device struct properties and the JSON keys (unless you use CodingKeys for mapping). For example:

  • If the JSON uses device_id but your model has id, add a coding key enum to bridge the gap:

    struct Device: Codable {
        let id: String
        
        enum CodingKeys: String, CodingKey {
            case id = "device_id"
        }
    }
    

  • Double-check that property types align: if the JSON returns id as a number, your model should use Int instead of String, or vice versa.

• Incorrect Success/Failure Logic in NetworkService
  Your NetworkService might be treating non-2xx HTTP responses (like 400 or 500 errors) as .Success, meaning the data contains an error JSON instead of a valid Device object. Verify that networkRequest only marks responses as .Success when the HTTP status code falls in the 200-299 range.

• Swift 4/Xcode 9 Compatibility Bugs
  Early versions of Xcode 9 had minor bugs with Codable handling. Make sure you're running the latest Xcode 9 update (9.4.1) to rule out framework-level issues.

• Outdated PushPad Pod
  Check if your PushPad Pod version is compatible with Swift 4 and Xcode 9. Run pod outdated to see if there's an update that might resolve decoding-related bugs.

Quick Validation Tip #

Copy the raw JSON string from the print statement and paste it into a .json file, then open it in Xcode—its built-in JSON viewer will highlight structure issues and make it easy to compare against your Device model.

内容的提问来源于stack exchange，提问作者JAN ERIK Meidell