September 2015
Intermediate to advanced
250 pages
6h 40m
English
Content preview from Pragmatic Scala
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.
Variance of Parameterized Type
Scala prevented us from assigning a reference of ArrayList[Int] to a reference of ArrayList[Any] in Type Inference for Generics and Collections. That’s a good thing; in general a collection of derived should not be assignable to a collection of base. However, there are times when we want some lenience to that rule. In those situations, we can ask Scala to permit otherwise invalid conversions. Tighten your seat belts—we’re in for a fun, but intense, ride.
Covariance and Contravariance
Scala will stop at compile time any conversions that may potentially lead to runtime failures. Specifically, as an example, it prevents the following code from compiling:
| | var arr1 = new Array[Int](3) |
| | var arr2: Array ... |
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