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    <blockquote> <p>Why do I have to declare "static" in the class?</p> </blockquote> <p>Because instance variables/methods can't be <code>const</code>. This would mean their value could be different per instance, which can't be the case for compile-time constants. <a href="https://www.dartlang.org/docs/dart-up-and-running/contents/ch02.html#ch02-final-const" rel="nofollow">(Source)</a></p> <blockquote> <p>Why can't I declare a "top level" const as "static"?</p> </blockquote> <p>The <code>static</code> modifier marks variables/methods as class-wide (same value for every instance of the class). Top-level stuff is application-wide and doesn't belong to any class, so marking them as class-wide doesn't make any sense and is not allowed. <a href="https://www.dartlang.org/docs/dart-up-and-running/contents/ch02.html#ch02-class-vars-and-methods" rel="nofollow">(Source)</a></p> <blockquote> <p>What is the best or only way to declare compile-time values that cannot be altered?</p> </blockquote> <p>You are already doing it - add <code>static</code> when defining class constants. Don't add it when defining top-level constants. Also, use <code>const</code>. <code>final</code> vars aren't compile-time values.</p> <blockquote> <p>What is the difference between [source code with different constant definitions omitted]</p> </blockquote> <p><code>static const</code> and <code>const</code> is the pretty much the same, usage depends on context. The difference between <code>const</code> and <code>final</code> is that <code>const</code> are compile-time constants - they can only be initialized using literal values (or expressions constisting of operators and literal values) and can't be changed. <code>final</code> variables also can't be changed after being initialized, but they are basically normal variables. This means any kind of expression can be used, and the value can be a different one for every class instance:</p> <pre class="lang-dart prettyprint-override"><code>import "dart:math"; Random r = new Random(); int getFinalValue() { return new Random().nextInt(100); } class Test { // final variable per instance. final int FOO = getFinalValue(); // final variable per class. "const" wouldn't work here, getFinalValue() is no literal static final int BAR = getFinalValue(); } // final top-level variable final int BAZ = getFinalValue(); // again, this doesn't work, because static top-level elements don't make sense // static final int WAT = getFinalValue(); void main() { Test a = new Test(); print(Test.BAR); print(BAZ); // different from Test.BAR print(a.FOO); a = new Test(); print(Test.BAR); // same as before print(BAZ); // same as before print(a.FOO); // not the same as before, because it is another instance, // initialized with another value // but this would still be a syntax error, because the variable is final. // a.FOO = 42; } </code></pre> <p>I hope this helped, and I didn't descibe it too confusing. :]</p>
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    1. COYes, I think that explains it well thanks. I'll come back to it later.
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    2. COAlso note that final variables are initialized lazily on first access.
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      1. USFlorian Loitsch
 

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