Here is a list of red-flags (in no particular order) that could indicate that a function is too long: Deeply nested control structures: e.g. for-loops 3 levels deep or even just 2 levels deep with nested if-statements that have complex conditions. Too many state-defining parameters: By state-defining parameter, I mean a function parameter that guarantees … Read more
Let’s say you create a higher order function that takes a lambda of type () -> Unit (no parameters, no return value), and executes it like so: fun nonInlined(block: () -> Unit) { println(“before”) block() println(“after”) } In Java parlance, this will translate to something like this (simplified!): public void nonInlined(Function block) { System.out.println(“before”); block.invoke(); … Read more
Return a tuple: func getTime() -> (Int, Int, Int) { … return ( hour, minute, second) } Then it’s invoked as: let (hour, minute, second) = getTime() or: let time = getTime() println(“hour: \(time.0)”)
Say you have a download function to download a file from network, and want to be notified when download task has finished. typealias CompletionHandler = (success:Bool) -> Void func downloadFileFromURL(url: NSURL,completionHandler: CompletionHandler) { // download code. let flag = true // true if download succeed,false otherwise completionHandler(success: flag) } // How to use it. downloadFileFromURL(NSURL(string: … Read more
Since default arguments are not supported you can get a similar behavior using Option<T> fn add(a: Option<i32>, b: Option<i32>) -> i32 { a.unwrap_or(1) + b.unwrap_or(2) } This accomplishes the objective of having the default value and the function coded only once (instead of in every call), but is of course a whole lot more to … Read more
Note that the FAQ does mention consistency Next is consistency. If some of the methods of the type must have pointer receivers, the rest should too, so the method set is consistent regardless of how the type is used. See the section on method sets for details. As mentioned in this thread: The rule about … Read more
The colon is for implementing methods that pass self as the first parameter. So x:bar(3,4)should be the same as x.bar(x,3,4).
Yes, consider some of these examples: package main import “fmt” // convert types take an int and return a string value. type convert func(int) string // value implements convert, returning x as string. func value(x int) string { return fmt.Sprintf(“%v”, x) } // quote123 passes 123 to convert func and returns quoted string. func quote123(fn … Read more
A function returns a value and a procedure just executes commands. The name function comes from math. It is used to calculate a value based on input. A procedure is a set of commands which can be executed in order. In most programming languages, even functions can have a set of commands. Hence the difference … Read more
Jim has got this pretty much covered in his blog post, but I’m posting a briefing here for reference. First, let’s see what the Scala Specification tell us. Chapter 3 (types) tell us about Function Types (3.2.9) and Method Types (3.3.1). Chapter 4 (basic declarations) speaks of Value Declaration and Definitions (4.1), Variable Declaration and … Read more