attempt.swift

/// consists of file path, line number, error tuple
public typealias CommonErrorHandlerType = (String, Int, ErrorType) -> Void

/// Default error handler prints context and error
public let defaultCommonErrorHandler: CommonErrorHandlerType = {
    filePath, lineNumber, error in
    let trimmedFileName: String = (filePath as NSString).lastPathComponent
    print("Error \(trimmedFileName):\(lineNumber) \(error)")
}

/// Replacement for `try?` that introduces an error handler
/// The default error handler prints an error before returning nil
public func attempt<T>(
    file fileName: String = __FILE__,
    line lineNumber: Int = __LINE__,
    crashOnError: Bool = false,
    errorHandler: CommonErrorHandlerType = defaultCommonErrorHandler,
    // Thanks, http://twitter.com/Kametrixom/status/709809975447707648
    @noescape closure: () throws -> T) -> T? { 
        
        do {
            // Return executes only if closure succeeds, returning T
            return try closure()
            
        } catch {
            // Emulate try! by crashing
            if crashOnError {
                print("Fatal error \(fileName):\(lineNumber): \(error)")
                fatalError()
            }
            
            // Execute error handler and return nil
            errorHandler(fileName, lineNumber, error)
            return nil
        }
}