Quick Answer

Throwing, propagating, and catching errors in Swift

Understanding the Issue

Swift errors are represented by types conforming to the Error protocol. Functions can throw errors, and callers must handle them with do-try-catch or propagation.

The Problem

This code demonstrates the issue:

Swift Error 
// Problem: No error handling
let data = try parse(json: invalidJson) // Compiler error

The Solution

Here's the corrected code:

Swift Fixed 
// Solution: do-try-catch block
do {
    let data = try parse(json: jsonString)
    print(data)
} catch ParsingError.invalidFormat {
    print("Invalid JSON format")
} catch {
    print("Other error: (error)")
}

// Alternative: try? for optional result
if let data = try? parse(json: jsonString) {
    // handle data
}

Key Takeaways

Use do-try-catch for comprehensive error handling or try? when errors can be safely ignored.