Was getting the following errors when calling AVAssetImageGenerator generateCGImagesAsynchronously. The stream in question was an HLS stream. When I switched to using the AVURLAsset of an MP4, the error disappeared.

With Apple-supplied HLS stream:

Error Domain=AVFoundationErrorDomain Code=-11819 "Cannot Complete Action" UserInfo={NSLocalizedRecoverySuggestion=Try again later., NSLocalizedDescription=Cannot Complete Action, NSUnderlyingError=0x1c0057850 {Error Domain=NSOSStatusErrorDomain Code=-12178 "(null)"}}

With another HLS stream generated by a video hosting provider:

Error Domain=AVFoundationErrorDomain Code=-11800 "The operation could not be completed" UserInfo={NSLocalizedFailureReason=An unknown error occurred (-12436), NSLocalizedDescription=The operation could not be completed, NSUnderlyingError=0x1c4a57e20 {Error Domain=NSOSStatusErrorDomain Code=-12436 "(null)"}}

View ProtocolExtensions.swift
protocol Protocol {
func methodInProtocol() -> String
extension Protocol {
func methodInProtocol() -> String {
return "Protocol"
func methodOnExtension() -> String {
View Mutated.swift
protocol Mutatable {}
extension Mutatable {
func mutated(f: (inout Self) -> Void) -> Self {
var copy = self
return copy
View NSTextStorageSubclass.swift
import Cocoa
class SomeTextStorage: NSTextStorage {
private var storage: NSMutableAttributedString
override init() {
storage = NSMutableAttributedString(string: "", attributes: nil)
View Completion.swift
final class Completion<R> {
private let closure: (R) -> Void
private var cancelled = false
/// `closure` is called upon completion, if not cancelled.
init(closure: (R) -> Void) {
self.closure = closure
View PivotalTrackerMarkdownLink.js
View KeyValueObserver.swift
import Foundation
/// Helper object for more Swift-like KVO. To create, call NSObject.addObserverForKeyPath(_:handler:).
class KeyValueObserver: NSObject {
private weak var observing: NSObject?
private var keyPath: String
private var handler: () -> Void
private init(observing: NSObject, keyPath: String, handler: () -> Void) {
View ErrorType+LocalizedDescription.swift
extension ErrorType {
var myLocalizedDescription: String {
if self.dynamicType == NSError.self {
return ((self as Any) as! NSError).localizedDescription
else {
return "\(self)"
View DispatchSyncThrows.swift
import Foundation
/// Call a throwing block synchronously.
func dispatch_sync(queue: dispatch_queue_t, block: () throws -> ()) throws {
var error: ErrorType?
dispatch_sync(queue) {
do {
try block()
} catch let caughtError {
error = caughtError
View demo_foreign.c
#include <assert.h>
#include <string.h>
#include <stdio.h>
#include "wren.h"
void logFromWren(WrenVM *vm) {
//double x = wrenGetArgumentDouble(vm, 0); // returns 0 in this setting
const char *message = wrenGetArgumentString(vm, 1);
printf("logFromWren: %s\n", message);