4 ms·

Swift Language Highlights: An Objective-C Developer’s Perspective

54 points by davidbarker 12y ago

afternooner 12y ago
On containers, while it's entirely possible to constrain the type, it's also possible to use AnyObject var example = Dictionary<Int,AnyObject>() I'll miss the duck typing, but having bought my house off C# work, I can work with this.
- steveklabnik 12y ago
  The first time I saw this idea was in Rust, which calls its type Any. I haven't seen the need to use it yet, but this seems like a decent case. What other languages have this? How is it often used? I've never heard of a similar type in, say, Haskell.
  - Xlythe 12y ago
    In Java, everything extends Object, so something like List<Object> will let you put anything you want into it. I should play with more languages, I didn't realize that was an uncommon feature.
    - steveklabnik 12y ago
      Oh, duh, of course that's true. For some reason "the parent class of every class" is different than "a type explicitly for any type" in my brain.
      - noblethrasher 12y ago
        >For some reason "the parent class of every class" is different than "a type explicitly for any type" in my brain. Good, because types and classes are different things despite what languages like Java and my beloved C# would have us to think.
        brandonbloom 12y ago
        To clarify: "Object" as in Java is a type for any tagged box type. Primitives, such as "int", don't derive from Object, but can be promoted to a corresponding boxed type, such as "Integer". The story is a little more complex in C#, where ValueType derives from Object and "value types", both primitive and user-defined, are truly subclasses of Object. Types not derived from ValueType are considered reference types.
    - pjmlp 12y ago
      This is a consequence of lack of generics and comes from Smalltalk. In languages where genericity is supported, you don't need a common base class with a pre-defined set of methods, as you can give type constraints. Java could also have done it with interfaces, but those were the days OO was becoming mainstream and interface (component) based programming wasn't yet well understood.
  - dantiberian 12y ago
    Haskell does have an Any type, but because of it's functional nature it's not as useful as in an OO language. http://stackoverflow.com/questions/6479444/is-there-a-type-any-in-haskell http://stackoverflow.com/questions/6479444/is-there-a-type-a...
  - biftek 12y ago
    Julia also has a useful Any type.
  - p4lindromica 12y ago
    Scala also has a unified type system. The root is Any. AnyVal (primitives) and AnyRef (AKA java's Object) extend Any. Int is always Int instead of thinking about int and Integer. Scala handles boxing when the JVM requires it, but it is invisible to the programmer.
Roboprog 12y ago
Did I read that right about the range operators: triple-dot (...) is like the inclusive range that perl, python, ruby (etc?) denote with double-dot (..), and in swift double-dot (..) is actually a special range operator that excludes the upper limit? If so, that seems backwards, and too late to fix :-( (not huge, but unfortunate)
- hrabago 12y ago
  I can't talk about the comparison to perl/python/ruby, but yes, using the triple dot includes the upper limit, and using the double-dot excludes it. For the typical (for var i=0; i < count-1; i++) scenario, you'd using the double dot (i in 0..count).
- roryokane 12y ago
  I always thought that Ruby had it backwards, so I’m glad it’s different in Swift. I think it makes more sense for the triple-dot ... range to mean an inclusive range, because you type an extra dot at the end compared to the double-dot .. range, and that extra dot means that the range includes an extra number on the end.
- jacobolus 12y ago
  Python has much more sensible range operations (based on slice syntax for array slices, or the arguments to the build-in 'range' function) that are unrelated to this. Ruby (and coffeescript, and perhaps perl) uses a..b to indicate a closed range (i.e. including b), or a...b to indicate a half-closed range (not including b). Swift seems to do the opposite. My guess for how ruby (or predecessors) came up with this was by copying bash (or sh?), which has only the .. version. To be honest, the .. vs. ... distinction is really confusing and error-prone, and a bad bit of syntax to include in any language, period.
  - andybak 12y ago
    First thing I looked for in Swift was support for Python's slicing syntax. It's a shame they decided against using that.
- 12y ago

54 points by davidbarker 12y ago

On containers, while it's entirely possible to constrain the type, it's also possible to use AnyObject var example = Dictionary<Int,AnyObject>() I'll miss the duck typing, but having bought my house off C# work, I can work with this.

steveklabnik 12y ago
The first time I saw this idea was in Rust, which calls its type Any. I haven't seen the need to use it yet, but this seems like a decent case. What other languages have this? How is it often used? I've never heard of a similar type in, say, Haskell.
- Xlythe 12y ago
  In Java, everything extends Object, so something like List<Object> will let you put anything you want into it. I should play with more languages, I didn't realize that was an uncommon feature.
  - steveklabnik 12y ago
    Oh, duh, of course that's true. For some reason "the parent class of every class" is different than "a type explicitly for any type" in my brain.
    - noblethrasher 12y ago
      >For some reason "the parent class of every class" is different than "a type explicitly for any type" in my brain. Good, because types and classes are different things despite what languages like Java and my beloved C# would have us to think.
      - brandonbloom 12y ago
        To clarify: "Object" as in Java is a type for any tagged box type. Primitives, such as "int", don't derive from Object, but can be promoted to a corresponding boxed type, such as "Integer". The story is a little more complex in C#, where ValueType derives from Object and "value types", both primitive and user-defined, are truly subclasses of Object. Types not derived from ValueType are considered reference types.
  - pjmlp 12y ago
    This is a consequence of lack of generics and comes from Smalltalk. In languages where genericity is supported, you don't need a common base class with a pre-defined set of methods, as you can give type constraints. Java could also have done it with interfaces, but those were the days OO was becoming mainstream and interface (component) based programming wasn't yet well understood.
- dantiberian 12y ago
  Haskell does have an Any type, but because of it's functional nature it's not as useful as in an OO language. http://stackoverflow.com/questions/6479444/is-there-a-type-any-in-haskell http://stackoverflow.com/questions/6479444/is-there-a-type-a...
- biftek 12y ago
  Julia also has a useful Any type.
- p4lindromica 12y ago
  Scala also has a unified type system. The root is Any. AnyVal (primitives) and AnyRef (AKA java's Object) extend Any. Int is always Int instead of thinking about int and Integer. Scala handles boxing when the JVM requires it, but it is invisible to the programmer.

Roboprog 12y ago

Did I read that right about the range operators: triple-dot (...) is like the inclusive range that perl, python, ruby (etc?) denote with double-dot (..), and in swift double-dot (..) is actually a special range operator that excludes the upper limit? If so, that seems backwards, and too late to fix :-( (not huge, but unfortunate)

hrabago 12y ago
I can't talk about the comparison to perl/python/ruby, but yes, using the triple dot includes the upper limit, and using the double-dot excludes it. For the typical (for var i=0; i < count-1; i++) scenario, you'd using the double dot (i in 0..count).
roryokane 12y ago
I always thought that Ruby had it backwards, so I’m glad it’s different in Swift. I think it makes more sense for the triple-dot ... range to mean an inclusive range, because you type an extra dot at the end compared to the double-dot .. range, and that extra dot means that the range includes an extra number on the end.
jacobolus 12y ago
Python has much more sensible range operations (based on slice syntax for array slices, or the arguments to the build-in 'range' function) that are unrelated to this. Ruby (and coffeescript, and perhaps perl) uses a..b to indicate a closed range (i.e. including b), or a...b to indicate a half-closed range (not including b). Swift seems to do the opposite. My guess for how ruby (or predecessors) came up with this was by copying bash (or sh?), which has only the .. version. To be honest, the .. vs. ... distinction is really confusing and error-prone, and a bad bit of syntax to include in any language, period.
- andybak 12y ago
  First thing I looked for in Swift was support for Python's slicing syntax. It's a shame they decided against using that.
12y ago