Tutorial by Examples: d

ElementAt will return the item at index n. If n is not within the range of the enumerable, throws an ArgumentOutOfRangeException. int[] numbers = { 1, 2, 3, 4, 5 }; numbers.ElementAt(2); // 3 numbers.ElementAt(10); // throws ArgumentOutOfRangeException ElementAtOrDefault will return the item...

Streams of elements usually do not allow access to the index value of the current item. To iterate over an array or ArrayList while having access to indexes, use IntStream.range(start, endExclusive). String[] names = { "Jon", "Darin", "Bauke", "Hans", "M...

Install haveged (example sudo apt-get install haveged) to speed up the random byte process. Then: gpg --gen-key gpg --list-keys outputs: pub 2048R/NNNNNNNN 2016-01-01 uid Name <[email protected]> sub 2048R/xxxxxxxx 2016-01-01 Then publish: gpg --keyserver pgp.mi...

var myData = [ { name: "test1", value: "ok" }, { name: "test2", value: "nok" } ] // We have to select elements (here div.samples) // and assign data. The second parameter of data() is really important, // it will determine the "key" t...

Tuples in Python are values separated by commas. Enclosing parentheses for inputting tuples are optional, so the two assignments a = 1, 2, 3 # a is the tuple (1, 2, 3) and a = (1, 2, 3) # a is the tuple (1, 2, 3) are equivalent. The assignment a = 1, 2, 3 is also called packing because it...

In a normal mathematical coordinate system, the point x=0, y=0 is at the lower left corner of the graph. But in the SVG coordinate system, this (0,0) point is at the top left corner of the ‘canvas’, it is sort of similar to CSS when you specify the position to absolute/fix and use top and left to co...

To generate an ActiveRecord model that automagically creates the correct db migrations & boilerplate test files for your model, enter this command rails generate model NAME column_name:column_type 'NAME' is the name of the model. 'field' is the name of the column in the DB table and 'type' i...

Components in Vue are like widgets. They allow us to write reusable custom elements with desired behavior. They are nothing but objects which can contain any/all of the options that the root or any Vue instance can contain, including an HTML template to render. Components consist of: HTML marku...

When you bind a service to your application credentials become available through the VCAP_SERVICES environment variable. This environment variable contains JSON containing the credentials for all bound services. Example VCAP_SERVICES environment variable { "push-reappt": [ { ...

#include <SoftwareSerial.h> // its always better to change the default tx and rx as the may interfere with other process in future. // configure tx , rx by defualt they will be 0 and 1 in arduino UNO SoftwareSerial blue(3,2); void setup() { // preferred baud rate/data transfer rat...

CREATE TABLE #TEST ( Id INT, Name VARCHAR(10) ) Insert Into #Test select 1,'A' Union All Select 1,'B' union all Select 1,'C' union all Select 2,'D' Below is the output of above table,As you can see Id Column is repeated three times.. Id Name 1 A 1 B 1 C 2 D Now...

The command prompt comes pre-installed on all Windows NT, Windows CE, OS/2 and eComStation operating systems, and exists as cmd.exe, typically located in C:\Windows\system32\cmd.exe On Windows 7 the fastest ways to open the command prompt are: Press , type "cmd" and then press Enter....

Preface You'll need node >= 4 and express 4 for this project. You can get the latest node distribution from their download page. Before this tutorial, you should initialize your node project by running $ npm init from the command line and filling in the information you want. Note that you c...

You can add your own validations adding new classes inheriting from ActiveModel::Validator or from ActiveModel::EachValidator. Both methods are similar but they work in a slightly different ways: ActiveModel::Validator and validates_with Implement the validate method which takes a record as an arg...

This example is a snippet taken from the Extending Django User Profile like a Pro from django.db import models from django.contrib.auth.models import User from django.db.models.signals import post_save class UserProfile(models.Model): user = models.OneToOneField(User, related_name='user'...

The policy builder allows you to build sophisticated policies. app.UseCors(builder => { builder.WithOrigins("http://localhost:5000", "http://myproductionapp.com") .WithMethods("GET", "POST", "HEAD") .WithHeaders(&quo...

Open the psql command line tool connected to the database where your table is. Then type the following command: \d tablename To get extended information type \d+ tablename If you have forgotten the name of the table, just type \d into psql to obtain a list of tables and views in the current ...

Date always have a different format, they can be parsed using a specific parse_dates function. This input.csv: 2016 06 10 20:30:00 foo 2016 07 11 19:45:30 bar 2013 10 12 4:30:00 foo Can be parsed like this : mydateparser = lambda x: pd.datetime.strptime(x, "%Y %m %d %H:%M:%S...

Redux is the most common state management library used with React-Native. The following example demonstrates how to use the fetch API and dispatch changes to your applications state reducer using redux-thunk. export const fetchRecipes = (action) => { return (dispatch, getState) => { f...

GridViews allow commands to be sent from a GridView row. This is useful for passing row-specific information into an event handler as command arguments. To subscribe to a command event: <asp:GridView ID="GridView1" ... OnRowCommand="GridView1_RowCommand"> Buttons are t...