Tutorial by Examples: b

help <command> This will display the Bash help (manual) page for the specified built-in. For example, help unset will show: unset: unset [-f] [-v] [-n] [name ...] Unset values and attributes of shell variables and functions. For each NAME, remove the corresponding variable or ...

An example of a RLMObject base model class that uses a primary key and some generic default properties. Subclasses can then set metadata specific to their needs. @interface BaseModel : RLMObject @property NSString *uuid; @property NSString *metadata; @end @implementation BaseModel + (N...

Java provides the instanceof operator to test if an object is of a certain type, or a subclass of that type. The program can then choose to cast or not cast that object accordingly. Object obj = Calendar.getInstance(); long time = 0; if(obj instanceof Calendar) { time = ((Calendar)obj).ge...

dput() and dget() The easiest way to share a (preferable small) data frame is to use a basic function dput(). It will export an R object in a plain text form. Note: Before making the example data below, make sure you're in an empty folder you can write to. Run getwd() and read ?setwd if you need t...

Package reproducibility is a very common issue in reproducing some R code. When various packages get updated, some interconnections between them may break. The ideal solution for the problem is to reproduce the image of the R code writer's machine on your computer at the date when the code was writt...

In Python 2, writing directly to a file handle returns None: Python 2.x2.3 hi = sys.stdout.write('hello world\n') # Out: hello world type(hi) # Out: <type 'NoneType'> In Python 3, writing to a handle will return the number of characters written when writing text, and the number of by...

Setting up key value observing. In this case, we want to observe the contentOffset on an object that our observer owns // // Class to observe // @interface XYZScrollView: NSObject @property (nonatomic, assign) CGPoint contentOffset; @end @implementation XYZScrollView @end // // Clas...

Install module and read docs npm i formidable@latest Example of server on 8080 port var formidable = require('formidable'), http = require('http'), util = require('util'); http.createServer(function(req, res) { if (req.url == '/upload' && req.method.toLowerCase() == 'pos...

Interface: public interface FooService { public int doSomething(); } Class: @Service public class FooServiceImpl implements FooService { @Override public int doSomething() { //Do some stuff here return 0; } } It should be noted that a class must imple...

public void iterate(final String dirPath) throws IOException { final DirectoryStream<Path> paths = Files.newDirectoryStream(Paths.get(dirPath)); for (final Path path : paths) { if (Files.isDirectory(path)) { System.out.println(path.getFileName()); } } ...

Once you have created your gem to publish it you have to follow a few steps: Build your gem with gem build <gem name>.gemspec (the gemspec file must exist) Create a RubyGems account if you do not already have one here Check to make sure that no gems exist that share your gems name Publis...

def say_hi MESSAGE = "Hello" puts MESSAGE end The above code results in an error: SyntaxError: (irb):2: dynamic constant assignment.

Local variables (unlike the other variable classes) do not have any prefix local_variable = "local" p local_variable # => local Its scope is dependent on where it has been declared, it can not be used outside the "declaration containers" scope. For example, if a local va...

Class variables have a class wide scope, they can be declared anywhere in the class. A variable will be considered a class variable when prefixed with @@ class Dinosaur @@classification = "Like a Reptile, but like a bird" def self.classification @@classification ...

Global variables have a global scope and hence, can be used everywhere. Their scope is not dependent on where they are defined. A variable will be considered global, when prefixed with a $ sign. $i_am_global = "omg" class Dinosaur def instance_method p "global vars ca...

Instance variables have an object wide scope, they can be declared anywhere in the object, however an instance variable declared on class level, will only be visible in the class object. A variable will be considered an instance variable when prefixed with @. Instance variables are used to set and g...

public void SaveNewEmployee(Employee newEmployee) { // best practice - wrap all database connections in a using block so they are always closed & disposed even in the event of an Exception // best practice - retrieve the connection string by name from the app.config or web.config (dep...

The easiest way to install and manage various versions of Ruby with rbenv is to use the ruby-build plugin. First clone the rbenv repository to your home directory: $ git clone https://github.com/rbenv/rbenv.git ~/.rbenv Then clone the ruby-build plugin: $ git clone https://github.com/rbenv/rub...

Suppose the make fails: $ make Launch it instead with make VERBOSE=1 to see the commands executed. Then directly run the linker or compiler command that you'll see. Try to make it work by adding necessary flags or libraries. Then figure out what to change, so CMake itself can pass correct argum...

Reflection is useful when it is properly used for right purpose. By using reflection, you can access private variables and re-initialize final variables. Below is the code snippet, which is not recommended. import java.lang.reflect.*; public class ReflectionDemo{ public static void main(St...