Tutorial by Examples: call

Given a function that accepts a Node-style callback, fooFn(options, function callback(err, result) { ... }); you can promisify it (convert it to a promise-based function) like this: function promiseFooFn(options) { return new Promise((resolve, reject) => fooFn(options, (err, re...

The first operand must be a function pointer (a function designator is also acceptable because it will be converted to a pointer to the function), identifying the function to call, and all other operands, if any, are collectively known as the function call's arguments. Evaluates into the return valu...

Normally, a Docker container persists after it has exited. This allows you to run the container again, inspect its filesystem, and so on. However, sometimes you want to run a container and delete it immediately after it exits. For example to execute a command or show a file from the filesystem. Dock...

$ docker images REPOSITORY TAG IMAGE ID CREATED SIZE hello-world latest 693bce725149 6 days ago 967 B postgres 9.5 0f3af79d8673 10 weeks ago 265.7 MB postgres ...

In Google Chrome, you can pause execution without needing to place breakpoints. Pause on Exception: While this button is toggled on, if your program hits an unhandled exception, the program will pause as if it had hit a breakpoint. The button can be found near Execution Controls and is useful for ...

In functions taking callable as an argument, you can also put a string with PHP built-in function. It's common to use trim as array_map parameter to remove leading and trailing whitespace from all strings in the array. $arr = [' one ', 'two ', ' three']; var_dump(array_map('trim', $arr)); ...

// Create an array with a fixed size and type. var array = new Uint8Array(5); // Generate cryptographically random values crypto.getRandomValues(array); // Print the array to the console console.log(array); crypto.getRandomValues(array) can be used with instances of the following classes...

Boilerplate code example override func viewDidLoad() { super.viewDidLoad() let myView = UIView() myView.backgroundColor = UIColor.blueColor() myView.translatesAutoresizingMaskIntoConstraints = false view.addSubview(myView) // Add constraints code here // ... ...

Callables are anything which can be called as a callback. Things that can be termed a "callback" are as follows: Anonymous functions Standard PHP functions (note: not language constructs) Static Classes non-static Classes (using an alternate syntax) Specific Object...

Consider we have a class Animal which has a child class Dog class Animal { public Animal() { Console.WriteLine("In Animal's constructor"); } } class Dog : Animal { public Dog() { Console.WriteLine("In Dog's constructor"); } ...

The null coalescing operator makes it easy to ensure that a method that may return null will fall back to a default value. Without the null coalescing operator: string name = GetName(); if (name == null) name = "Unknown!"; With the null coalescing operator: string name = GetN...

#include <stdlib.h> #include <lauxlib.h> #include <lua.h> #include <lualib.h> int main(void) { lua_State *lvm_hnd = lua_open(); luaL_openlibs(lvm_hnd); /* Load a standard Lua function from global table: */ lua_getglobal(lvm_hnd, "print&quot...

foo.h #ifndef FOO_DOT_H /* This is an "include guard" */ #define FOO_DOT_H /* prevents the file from being included twice. */ /* Including a header file twice causes all kinds */ /* of interesting problems.*/ /** * This is a functi...

While static constructors are always called before the first usage of a type it's sometimes useful to be able to force them to be called and the RuntimeHelpers class provide an helper for it: using System.Runtime.CompilerServices; // ... RuntimeHelpers.RunClassConstructor(typeof(Foo).TypeHand...

Hash has a default value for keys that are requested but don't exist (nil): a = {} p a[ :b ] # => nil When creating a new Hash, one can specify the default: b = Hash.new 'puppy' p b[ :b ] # => 'puppy' Hash.new also takes a block, which allows you to automatically create n...

class Animal def method_missing(method, *args, &block) "Cannot call #{method} on Animal" end end => Animal.new.say_moo > "Cannot call say_moo on Animal"

ProcedureName ProcedureName argument1, argument2 Call a procedure by its name without any parentheses. Edge case The Call keyword is only required in one edge case: Call DoSomething : DoSomethingElse DoSomething and DoSomethingElse are procedures being called. If the Call keyword was rem...

Call ProcedureName Call ProcedureName(argument1, argument2) The explicit call syntax requires the Call keyword and parentheses around the argument list; parentheses are redundant if there are no parameters. This syntax was made obsolete when the more modern implicit call syntax was added to VB. ...

By default the Python random module use the Mersenne Twister PRNG to generate random numbers, which, although suitable in domains like simulations, fails to meet security requirements in more demanding environments. In order to create a cryptographically secure pseudorandom number, one can use Syst...

public class Singleton { private readonly static Singleton instance = new Singleton(); private Singleton() { } public static Singleton Instance => instance; } This implementation is thread-safe because in this case instance object is initialized in the static constructor. The ...