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POCall methods between MainViewController.m and FlipsideViewController.m
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copied!<p><strong>Please see below edit for current (minor) issue</strong></p> <hr> <p><em>First of all, I'm new to this Obj C stuff, coming from javascript/PHP, I'm having a hard time dealing with the syntax so please bare with me here.</em> </p> <p>For hours now, I've been trying to <strong>call methods</strong> (methods right, not functions?) <strong>"between" the MainViewController.m and the FlipsideViewController.m</strong> -- from one file/class to another. </p> <p>I guess this is what's often referred to as "<strong>Call methods from another class</strong>". There are plenty of such questions around, I know, but I just can't get it to work properly.</p> <p>In my case, I have <strong>several user defined methods/functions in both above mentioned files</strong>. Sometimes, <strong>I need to call a method from within the FlipsideViewController.m that lies within the MainViewController.m File</strong>:</p> <pre><code>// in MainViewController.m - (void) calculateDays { //executes caluculations // inserts data into labels, etc } </code></pre> <p>If I want to call this function <strong>simply from within the same file</strong>, I just do:</p> <pre><code>[self calculateDays]; </code></pre> <p>That's easy, however, I want to call this function from within the FlipsideViewController.m file too, as well as vice versa. <strong>So how do I do this</strong>? <a href="https://stackoverflow.com/questions/3572448/objective-c-call-function-on-another-class">This</a>, <a href="https://stackoverflow.com/questions/7290156/call-a-class-method-from-within-that-class">this</a> and <a href="https://stackoverflow.com/questions/6830749/objective-c-calling-method-on-another-class">this</a> questions sort of answer it but it doesn't quite work to me. I'll explain why in just a second.</p> <p><strong>This is what I've tried and think should work:</strong></p> <pre><code>MainViewController *mvs = [[MainViewController alloc] init]; //alloc init MVC [mvs calculateDays]; //call "external" function </code></pre> <p>It gives me the error: <em>"Unknown type name MainViewController"</em>. So I assume I <strong>have to include/import</strong> it somehow for it to work (just like in javascript or PHP). So I include it in the FlipSideViewController.m class: </p> <pre><code> #import "MainViewController.h" </code></pre> <p>Great <em>no errors</em> so far. Then I try to <strong>compile/build</strong> it and runs into another error: <em>"clang: error: linker command failed with exit code 1 (use -v to see invocation)" "ld: 3 duplicate symbols for architecture armv7s"</em></p> <p>This <em>leads me to think</em> that <strong>importing the MainViewController like that isn't the way to go</strong> as I then import lots of other stuff that may interfere with some code in the FlipSideViewController class.</p> <p>I've <em>tried similar solutions</em> but nothing seems to work. Can anyone please explain to me what I'm doing wrong, and perhaps how to do this properly: Call methods between MainViewController.m and FlipsideViewController.m and vice versa.</p> <hr> <h2>Edit!</h2> <p>The <strong>proposed solution by H2CO3 did solve most of the issues</strong> (XCode bugged for a while and give me random errors which forced me to rebuild the entire project) but there's still this one thing that doesn't quite work: <strong>change the content of a UILabel (UIOutlet)</strong>. Please see if anyone of you can help me with this:</p> <p>When the method is called from within self (i.e. [self calculateDay]), the value is successfully inserted into the UILabel. When called from <strong>FlipsideViewController</strong>, the value to be inserted exists and is processed successfully, but can't be inserted into the UILabel. Please se below. </p> <p><strong>Some loggings:</strong></p> <pre><code>//method called from within self on viewDidLoad: [self calculateDay]; Processed value to update label with: 26 New value in outlet after having been inserted: 26 //method called from another (FlipsideViewController) class file: [mvs calculateDay]; Processed value to update label with: 26 New value in outlet after having been inserted: (null) /* This doesn't work either from that external file: [[mvs LabelName] setText:@"Hello, update label!"]; no errors but no display either */ </code></pre>

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