Rework interface definition to cleanly show openAccount. Add HINTS.md… #221
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… with note about mutable state. Refs exercism#214
| ## Hints | ||
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| This exercise is testing mutable state that can be accessed saftely from multiple threads. Scala provides a variety of ways to protect | ||
| mutable state. For developers familiar with Java concurrency, Scala can utilize the Java concurrency support such as the Java synchronized block. |
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Although this might already be some sort of spoiler you could add something like:
In Scala there are two ways to achieve mutable state: Use a "var" or a mutable object.
Two common mistakes here are:
- Do not use a "var" that is also a mutable object. One is enough, but not both together.
- Don't expose the "var" or mutable object to the outside world. So make them "private" and change the mutable object into immutable before you return it as a value.
One could also imagine a standard format with a separate section named "Common Pitfalls" or so.
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The suggested addendum by @abo64 seems like a good one, even though it is a bit of a spoiler.
| def incrementBalance(increment: Int): Option[Int] | ||
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| object Bank { |
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Why don't you want to use the companion object anymore?
Same for the file name. AFAIK the file name is always the same as the class/object to be implemented?
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Well, there is a Bank object being implemented of course, so that sort of makes sense. I usually named the files after the slug name, so for the BankAccount exercise, I would use BankAccount.scala.
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I changed the name for the Object from BankAccount to Bank. I didn't like having a BankAccount.openAccount function. It seems like a Bank should be opening accounts not a BankAccount. I thought about having a Bank.scala and BankAccount.scala. But, then I didn't like having 2 .scala files for the exercise..
name scala file after exercise name.
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I renamed Bank.scala to BankAccount.scala . At least now the source file is named to match the test cases file. Thanks! |
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Thanks! |
Refs BankAccount: not scala-ish enough? #214, Add hints to some exercises #220, Exercises do not provide a named file for the code to be delivered #137