https://homeostasis.scs.carleton.ca/wiki/index.php?action=history&feed=atom&title=Mobile_App_Development_2021W_Lecture_2 2026-04-09T13:13:44Z Revision history for this page on the wiki MediaWiki 1.42.1 https://homeostasis.scs.carleton.ca/wiki/index.php?title=Mobile_App_Development_2021W_Lecture_2&diff=22768&oldid=prev 2021-01-13T18:51:22Z

<p>Created page with &quot;==Video== Video from the lecture given on January 13, 2021 [https://homeostasis.scs.carleton.ca/~soma/mad-2021w/lectures/comp1601-2021w-lec02-20210113.m4v is now available]....&quot;</p> <p><b>New page</b></p><div>==Video==<br /> <br /> Video from the lecture given on January 13, 2021 [https://homeostasis.scs.carleton.ca/~soma/mad-2021w/lectures/comp1601-2021w-lec02-20210113.m4v is now available].<br /> <br /> ==Notes==<br /> <br /> &lt;pre&gt;<br /> Lecture 2<br /> ------------<br /> <br /> Readings<br /> Swift Basics:<br /> https://docs.swift.org/swift-book/LanguageGuide/TheBasics.html<br /> <br /> <br /> TA&#039;s will be keeping track of participation, posting in cuLearn periodically<br /> - if you think you weren&#039;t given credit for a lecture, talk to a TA<br /> - note we have a record between the Teams chat and audio from lectures<br /> <br /> SwiftUI terminology is similar to HTML/CSS, but this is because both come from terminology for GUIs, which come from terminology for printing (on paper)<br /> - look up TeX, in particular the TeXbook<br /> <br /> <br /> Is swiftUI front end?<br /> - will answer later<br /> <br /> Cross-platform development<br /> - environment I&#039;m developing for is different from the one in which I write code<br /> - developing on MacOS, but code will run on iOS<br /> - typically difficult, but with modern IDEs it is almost seamless<br /> - almost!<br /> <br /> @State variables<br /> - denotes variables that directly affect the interface<br /> - if their values change, the interface must be updated<br /> <br /> $ notation<br /> - in SwiftUI, means a binding to the variable should be passed<br /> - functionally it is like a pointer, but much safer, ie pass by reference not value<br /> <br /> &quot;if let X&quot;<br /> - checks whether X is nil or not<br /> - allows you to check for failed conversions, etc (e.g., if Double(s) finds that S<br /> was not a number)<br /> <br /> If you say &quot;F = Double(Fs)&quot;, F is not of type Double, it is of type Double?<br /> - it could be a double, or it could be nil<br /> - you can&#039;t use it until you check, or you force usage with !<br /> - don&#039;t use !, because if you are wrong your program crashes<br /> &lt;/pre&gt;<br /> <br /> ==Code==<br /> <br /> [https://homeostasis.scs.carleton.ca/~soma/mad-2021w/code/lec02.zip lec02 xcode project]</div>

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