# 📚 Official Books **URL:** https://forums.kodeco.com/c/books/6.md?page=73 [Latest](https://forums.kodeco.com/latest.md) · [Categories](https://forums.kodeco.com/categories.md) · [Tags](https://forums.kodeco.com/tags.md) **Page:** 74 --- ## [Chapter 5: Confusion Matrix visualization](https://forums.kodeco.com/t/chapter-5-confusion-matrix-visualization/103917)
**Author:** [@chlkdst](https://forums.kodeco.com/u/chlkdst)\ **Replies:** 2\ **Last updated:** [April 3, 2020, 3:37pm UTC](https://forums.kodeco.com/t/chapter-5-confusion-matrix-visualization/103917 "2020-04-03T15:37:07Z")
Hi all, I’m new at Python, thus I’m not very familiar with its syntax yet. I just want to confirm in the confusion matrix visualization part of the, in function compute\_confusion\_matrix(metrics, labels) there is this co… --- ## [Chapter 10 issue with the SpringNode](https://forums.kodeco.com/t/chapter-10-issue-with-the-springnode/102117)
**Author:** [@theraad](https://forums.kodeco.com/u/theraad)\ **Replies:** 2\ **Last updated:** [April 8, 2020, 7:52am UTC](https://forums.kodeco.com/t/chapter-10-issue-with-the-springnode/102117 "2020-04-08T07:52:21Z")
Hi, So i’ve been following the tutorials so far, and I’m nearly done with Chapter 10 (Adding levels 2 and 3 to CatNap). I’ve had an issue with the spring, for some reason whenever I generate the impulse from it, it for… --- ## [Chapter 7: General question about background](https://forums.kodeco.com/t/chapter-7-general-question-about-background/103920)
**Author:** [@chris-rw](https://forums.kodeco.com/u/chris-rw)\ **Replies:** 4\ **Last updated:** [April 7, 2020, 6:58pm UTC](https://forums.kodeco.com/t/chapter-7-general-question-about-background/103920 "2020-04-07T18:58:46Z")
I’m about to finish chapter 7 and my Bullseye app is working great. I’ve been fiddling around with some code to get a better idea of how things work and I’m confused about calling background(). The developer documentat… --- ## [Chp 41 - UIImageView extension for downloading images error](https://forums.kodeco.com/t/chp-41-uiimageview-extension-for-downloading-images-error/103167)
**Author:** [@malamin](https://forums.kodeco.com/u/malamin)\ **Replies:** 2\ **Last updated:** [April 7, 2020, 9:41am UTC](https://forums.kodeco.com/t/chp-41-uiimageview-extension-for-downloading-images-error/103167 "2020-04-07T09:41:34Z")
I’m getting 2 errors on the following line: let data = try? Data(contentsOf: url),… Just adding the new file (UIImageView+DownloadImage.swift) to the project fires off the error. I even get them when I copy and paste th… --- ## [Chapter 08: Crossfade](https://forums.kodeco.com/t/chapter-08-crossfade/81807)
**Author:** [@maninsan](https://forums.kodeco.com/u/maninsan)\ **Replies:** 0\ **Last updated:** [September 15, 2019, 7:32pm UTC](https://forums.kodeco.com/t/chapter-08-crossfade/81807 "2019-09-15T19:32:04Z")
Hello there, Just noticed after completing Chapter 08 of iOS Apprentice that Crossfade animation applied only to Start Over is a bit strange with leaving myself with some feeling of incompleteness as I am not getting th… --- ## [Unit Tests for MVVM with Android Architecture Components](https://forums.kodeco.com/t/unit-tests-for-mvvm-with-android-architecture-components/95526)
**Author:** [@jabouzi](https://forums.kodeco.com/u/jabouzi)\ **Replies:** 1\ **Last updated:** [April 7, 2020, 9:18am UTC](https://forums.kodeco.com/t/unit-tests-for-mvvm-with-android-architecture-components/95526 "2020-04-07T09:18:40Z")
Hi there, I’m surprised that the book covers Unit Tests for MVVM with Data Binding Only! Are willing to fix this any soon and add Unit Tests for MVVM with Android Architecture Components? Thanks. --- ## [Double length pseudolanguage?](https://forums.kodeco.com/t/double-length-pseudolanguage/95148)
**Author:** [@amitsrivastava](https://forums.kodeco.com/u/amitsrivastava)\ **Replies:** 2\ **Last updated:** [April 7, 2020, 9:17am UTC](https://forums.kodeco.com/t/double-length-pseudolanguage/95148 "2020-04-07T09:17:10Z")
Can any one please tell me how to use double length pseudolanguage, i tried going to product and edit scheme and change it to double length pseudolanguage, but it does not show on either a real device or simulator, i am … --- ## [Chapter 8 - Errata](https://forums.kodeco.com/t/chapter-8-errata/98147)
**Author:** [@abunur](https://forums.kodeco.com/u/abunur)\ **Replies:** 3\ **Last updated:** [April 6, 2020, 9:10pm UTC](https://forums.kodeco.com/t/chapter-8-errata/98147 "2020-04-06T21:10:20Z")
You can also pass a number into the constructor for these types, for example, to create an array of zeros. val zeros = DoubleArray(4) // 0.0, 0.0, 0.0, 0.0 The text implies the example will show passing a default val… --- ## [Chapter 10 - Feedback](https://forums.kodeco.com/t/chapter-10-feedback/104302)
**Author:** [@abunur](https://forums.kodeco.com/u/abunur)\ **Replies:** 1\ **Last updated:** [April 6, 2020, 8:36pm UTC](https://forums.kodeco.com/t/chapter-10-feedback/104302 "2020-04-06T20:36:09Z")
I feel Chapter 10 needs a bit of love in order to explain things more clearly. Starting with this bit of code and the following explanation: fun countingLambda(): () -\> Int { var counter = 0 val incrementCounter: (… --- ## [MathLibrary.swift](https://forums.kodeco.com/t/mathlibrary-swift/104230)
**Author:** [@tchelyzt](https://forums.kodeco.com/u/tchelyzt)\ **Replies:** 3\ **Last updated:** [April 6, 2020, 5:49pm UTC](https://forums.kodeco.com/t/mathlibrary-swift/104230 "2020-04-06T17:49:16Z")
Going through MathLibrary.swift (chapter 5) I noticed the following simple function static func identity() -\> float4x4 { matrix\_identity\_float4x4 } but it surprised me because there was no return keyword. I… --- ## [tvOS Apprentice Ch. 2 JS Error](https://forums.kodeco.com/t/tvos-apprentice-ch-2-js-error/93821)
**Author:** [@wbalthrop](https://forums.kodeco.com/u/wbalthrop)\ **Replies:** 2\ **Last updated:** [April 6, 2020, 5:45pm UTC](https://forums.kodeco.com/t/tvos-apprentice-ch-2-js-error/93821 "2020-04-06T17:45:20Z")
There appears to be a bug in Ch. 2. I have entered the code as instructed for main.js, and it throws can error in Safari. Ot says I’m missing a semi-colon, but they appear to all be there: My Code: App.onLaunch = funct… --- ## [Using @FetchRequest](https://forums.kodeco.com/t/using-fetchrequest/100735)
**Author:** [@wilsonilo](https://forums.kodeco.com/u/wilsonilo)\ **Replies:** 4\ **Last updated:** [April 6, 2020, 3:59pm UTC](https://forums.kodeco.com/t/using-fetchrequest/100735 "2020-04-06T15:59:50Z")
I’ve read the whole book and i loved it. Got stuck in a few parts but in general i’m happy with the content. I just felt a little underwhelmed on the specifics for @FetchRequest so i was hoping someone can help me out w… --- ## [Errata for Catalyst by Tutorials First Edition](https://forums.kodeco.com/t/errata-for-catalyst-by-tutorials-first-edition/79657)
**Author:** [@rwenderlich](https://forums.kodeco.com/u/rwenderlich)\ **Replies:** 9\ **Last updated:** [April 6, 2020, 3:29pm UTC](https://forums.kodeco.com/t/errata-for-catalyst-by-tutorials-first-edition/79657 "2020-04-06T15:29:17Z")
Creating this topic to catch any typos and bugs in the 1st Edition of Catalyst by Tutorials. --- ## [Problem with drag/drop chapter 3](https://forums.kodeco.com/t/problem-with-drag-drop-chapter-3/102183)
**Author:** [@wilsonilo](https://forums.kodeco.com/u/wilsonilo)\ **Replies:** 6\ **Last updated:** [April 6, 2020, 3:20pm UTC](https://forums.kodeco.com/t/problem-with-drag-drop-chapter-3/102183 "2020-04-06T15:20:38Z")
So after i finished chapter 3 and started doing testing my method was something like this func collectionView(\_ collectionView: UICollectionView, performDropWith coordinator: UICollectionViewDropCoordinator) { … --- ## [Xcode 11 hangs, project file appears faded in navigator, can't recover](https://forums.kodeco.com/t/xcode-11-hangs-project-file-appears-faded-in-navigator-cant-recover/104259)
**Author:** [@mayo](https://forums.kodeco.com/u/mayo)\ **Replies:** 1\ **Last updated:** [April 6, 2020, 2:35pm UTC](https://forums.kodeco.com/t/xcode-11-hangs-project-file-appears-faded-in-navigator-cant-recover/104259 "2020-04-06T14:35:27Z")
I’m working through Chapter 4 and for the second time Xcode 11 has just started hanging, claiming it’s no longer able to build the project even though command line builds with xcodebuild work fine. The project icon appea… --- ## [Chapter 18: Basic Authentication](https://forums.kodeco.com/t/chapter-18-basic-authentication/49761)
**Author:** [@axlroach](https://forums.kodeco.com/u/axlroach)\ **Replies:** 4\ **Last updated:** [April 6, 2020, 12:02pm UTC](https://forums.kodeco.com/t/chapter-18-basic-authentication/49761 "2020-04-06T12:02:28Z")
After following the instructions down through the end of the Basic Authentication section (through to page 298), when I use RESTed to attempt to create content, I get the following response: { "error": true, "re… --- ## [Robot Rampage - camera bumps upwards](https://forums.kodeco.com/t/robot-rampage-camera-bumps-upwards/103315)
**Author:** [@krillian](https://forums.kodeco.com/u/krillian)\ **Replies:** 2\ **Last updated:** [April 6, 2020, 11:10am UTC](https://forums.kodeco.com/t/robot-rampage-camera-bumps-upwards/103315 "2020-04-06T11:10:49Z")
Hi, Almost finished the tutorial for this game. Get a slightly weird bug, when I kill a robot and I am right in front of it, the camera shifts upwards as though I pressed jump and stays that way. Afterwards it remains … --- ## [Robot Rampage - No more ammo but robots still taking damage](https://forums.kodeco.com/t/robot-rampage-no-more-ammo-but-robots-still-taking-damage/103394)
**Author:** [@krillian](https://forums.kodeco.com/u/krillian)\ **Replies:** 3\ **Last updated:** [April 6, 2020, 11:10am UTC](https://forums.kodeco.com/t/robot-rampage-no-more-ammo-but-robots-still-taking-damage/103394 "2020-04-06T11:10:01Z")
Hi, Just noticed that when the ammo runs dry, if you still keep firing at the robots, the correct drygun sound is played but the robots continue to take damage. Can’t figure out if it’s an issue with my code or is it be… --- ## [Soyboy save function](https://forums.kodeco.com/t/soyboy-save-function/100747)
**Author:** [@ghostwolf](https://forums.kodeco.com/u/ghostwolf)\ **Replies:** 6\ **Last updated:** [April 6, 2020, 8:42am UTC](https://forums.kodeco.com/t/soyboy-save-function/100747 "2020-04-06T08:42:46Z")
For some reason when I build the game and play the times will not save. If I play the game in unity it does. The strange thing is that if I go back to the build version the times show up and it write new ones. I was wond… --- ## [Chapter 11 - Need to Set Working Directory?](https://forums.kodeco.com/t/chapter-11-need-to-set-working-directory/103060)
**Author:** [@barrymcbride](https://forums.kodeco.com/u/barrymcbride)\ **Replies:** 1\ **Last updated:** [April 6, 2020, 8:36am UTC](https://forums.kodeco.com/t/chapter-11-need-to-set-working-directory/103060 "2020-04-06T08:36:11Z")
When working through the chapter 11 tutorial on Stencil, I couldn’t get the app to find the “/public” directory until I set the working directory in XCode. This process is discussed here: https://www.raywenderlich.com/… --- ## [Chapter 44 - Landscape](https://forums.kodeco.com/t/chapter-44-landscape/102990)
**Author:** [@mcneils](https://forums.kodeco.com/u/mcneils)\ **Replies:** 1\ **Last updated:** [April 6, 2020, 8:17am UTC](https://forums.kodeco.com/t/chapter-44-landscape/102990 "2020-04-06T08:17:59Z")
I’m trying to customize a scroll view for a horizontal view for iPhone 11. I want to have the right side rectangles further away from the top-notch which I have done. The problem is that if I do a hard scroll to the left… --- ## [Chapter 3 - broken ARSCNView?](https://forums.kodeco.com/t/chapter-3-broken-arscnview/87471)
**Author:** [@srofe](https://forums.kodeco.com/u/srofe)\ **Replies:** 5\ **Last updated:** [April 6, 2020, 6:29am UTC](https://forums.kodeco.com/t/chapter-3-broken-arscnview/87471 "2020-04-06T06:29:08Z")
I am trying to work my way through ARKit by Tutorials and am up to Chapter 3. I am trying to run the starter project, but it crashes with the console error: 2019-11-08 12:16:48.289985+1000 ARPokerDice\[3172:1265809\] \*\*\* … --- ## [Chapter 5 - entering the Mac Catalyst App](https://forums.kodeco.com/t/chapter-5-entering-the-mac-catalyst-app/87344)
**Author:** [@thierry](https://forums.kodeco.com/u/thierry)\ **Replies:** 7\ **Last updated:** [April 6, 2020, 5:38am UTC](https://forums.kodeco.com/t/chapter-5-entering-the-mac-catalyst-app/87344 "2020-04-06T05:38:55Z")
Hi All, Following the steps in the book for enabling running the iOS app on the Mac, I got a long warning in the output window : BullsEyePlus\[2609:105114\] \[User Defaults\] Couldn’t write values for keys (ApplicationAcce… --- ## [Learning Core Data and the book is old and outdated](https://forums.kodeco.com/t/learning-core-data-and-the-book-is-old-and-outdated/102296)
**Author:** [@mazurick](https://forums.kodeco.com/u/mazurick)\ **Replies:** 13\ **Last updated:** [April 6, 2020, 1:40am UTC](https://forums.kodeco.com/t/learning-core-data-and-the-book-is-old-and-outdated/102296 "2020-04-06T01:40:43Z")
Hi, I am transitioning to Swift UI and just learning persistence. I just bought the book and its really old. Is there plans to write it for SwiftUI? --- ## [Chapter 21: LLDB is now on Python 3.X.Y](https://forums.kodeco.com/t/chapter-21-lldb-is-now-on-python-3-x-y/102477)
**Author:** [@sparklydust](https://forums.kodeco.com/u/sparklydust)\ **Replies:** 1\ **Last updated:** [April 6, 2020, 12:59am UTC](https://forums.kodeco.com/t/chapter-21-lldb-is-now-on-python-3-x-y/102477 "2020-04-06T00:59:29Z")
I came here to complain loudly that chapter 21 is not using Python 3.X.Y (I’m adding a comment as requested in the chapter). My question is: As the book hasn’t been updated since October 2018, are we going to have an up… --- ## [Chapter 7 - NavigationView](https://forums.kodeco.com/t/chapter-7-navigationview/102206)
**Author:** [@mengjun81](https://forums.kodeco.com/u/mengjun81)\ **Replies:** 1\ **Last updated:** [April 5, 2020, 10:52pm UTC](https://forums.kodeco.com/t/chapter-7-navigationview/102206 "2020-04-05T22:52:18Z")
V8.1 P251 After adding AboutView.swift to Bullseye, we started to add a navigationView to the ContentView. Following the steps, I put in var body: some View { NavigationView { … }.navigationViewStyle(.stack) howev… --- ## [iOS Apprentice 8th ed. co-author here!](https://forums.kodeco.com/t/ios-apprentice-8th-ed-co-author-here/91083)
**Author:** [@accordionguy](https://forums.kodeco.com/u/accordionguy)\ **Replies:** 3\ **Last updated:** [April 5, 2020, 9:46pm UTC](https://forums.kodeco.com/t/ios-apprentice-8th-ed-co-author-here/91083 "2020-04-05T21:46:51Z")
I’m Joey deVilla, and I wrote sections 1 and 2 of iOS Apprentice, 8th edition! I learned iOS programming from an earlier edition, and it was a dream come true to work on this revision. This is a quick post just to let y… --- ## [Ch 13: After editing an item, the edited row becomes unclickable](https://forums.kodeco.com/t/ch-13-after-editing-an-item-the-edited-row-becomes-unclickable/102552)
**Author:** [@tangobango](https://forums.kodeco.com/u/tangobango)\ **Replies:** 1\ **Last updated:** [April 5, 2020, 9:45pm UTC](https://forums.kodeco.com/t/ch-13-after-editing-an-item-the-edited-row-becomes-unclickable/102552 "2020-04-05T21:45:21Z")
I finally got the extensions to work by copying them directly into the project, but now there is a further problem: If I click on a row to open the edit item screen, once I return to the checklist screen that row become… --- ## [Chapter 13. After delete the last row, when try to edit item, the app will crash](https://forums.kodeco.com/t/chapter-13-after-delete-the-last-row-when-try-to-edit-item-the-app-will-crash/101963)
**Author:** [@ys\_xs](https://forums.kodeco.com/u/ys_xs)\ **Replies:** 1\ **Last updated:** [April 5, 2020, 9:44pm UTC](https://forums.kodeco.com/t/chapter-13-after-delete-the-last-row-when-try-to-edit-item-the-app-will-crash/101963 "2020-04-05T21:44:09Z")
I believe this is associated with the ’ forEach part’ in the ChecklistView but i cannot find why and how to fix it --- ## [Errata for Reactive Programming with Kotlin 1st Edition](https://forums.kodeco.com/t/errata-for-reactive-programming-with-kotlin-1st-edition/85353)
**Author:** [@macsimus](https://forums.kodeco.com/u/macsimus)\ **Replies:** 5\ **Last updated:** [April 5, 2020, 11:45am UTC](https://forums.kodeco.com/t/errata-for-reactive-programming-with-kotlin-1st-edition/85353 "2020-04-05T11:45:17Z")
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