Tutorial by Examples: f

addEventListener(Event.ENTER_FRAME,moveChild); function moveChild(e:Event):void { childMC.x++; if (childMC.x>1000) { gotoAndStop(2); } } This example will move the childMC (added to Main at design time) but will instantly throw a 1009 as soon as gotoAndStop() is invok...

prerequisite of scrapy installation: Python 2.7 or above 3.3 pip and setuptools Python packages. lxml OpenSSL. You can install Scrapy using pip. To install using pip run: pip install Scrapy Platform specific installation Anaconda This is the recommended way to install Scrapy. ...

interface ITable { // an indexer can be declared in an interface object this[int x, int y] { get; set; } } class DataTable : ITable { private object[,] cells = new object[10, 10]; /// <summary> /// implementation of the indexer declared in the interface //...

Get the list of inialized indexes in an array $ arr[2]='second' $ arr[10]='tenth' $ arr[25]='twenty five' $ echo ${!arr[@]} 2 10 25

Rescue from record not found error instead of showing an exception or white page: class ApplicationController < ActionController::Base # ... your other stuff here rescue_from ActiveRecord::RecordNotFound do |exception| redirect_to root_path, 404, alert: 'Record not found' en...

Arithmetic if statement allows one to use three branches depending on the result of an arithmetic expression if (arith_expr) label1, label2, label3 This if statement transfers control flow to one of the labels in a code. If the result of arith_expr is negative label1 is involved, if the result i...

This validation restricts the insertion of only numeric values. class Player < ApplicationRecord validates :points, numericality: true validates :games_played, numericality: { only_integer: true } end Besides :only_integer, this helper also accepts the following options to add constrai...

This helper validates that the attribute's value is unique right before the object gets saved. class Account < ApplicationRecord validates :email, uniqueness: true end There is a :scope option that you can use to specify one or more attributes that are used to limit the uniqueness check: ...

This helper validates that the specified attributes are not empty. class Person < ApplicationRecord validates :name, presence: true end Person.create(name: "John").valid? # => true Person.create(name: nil).valid? # => false You can use the absence helper to validate th...

class Person < ApplicationRecord validates :name, length: { minimum: 2 } validates :bio, length: { maximum: 500 } validates :password, length: { in: 6..20 } validates :registration_number, length: { is: 6 } end The possible length constraint options are: :minimum - The attribut...

The special attribute __name__ of a function, class or module is a string containing its name. import os class C: pass def f(x): x += 2 return x print(f) # <function f at 0x029976B0> print(f.__name__) # f print(C) # <class '__main__.C'> print(C.__name__...

While it might seem counterintuitive, you can use logical operators to determine whether or not a statement is run. For instance: File.exist?(filename) or STDERR.puts "#{filename} does not exist!" This will check to see if the file exists and only print the error message if it doesn't....

First: The path structure If you don't have it you need to create the middleware folder within your app following the structure: yourproject/yourapp/middleware The folder middleware should be placed in the same folder as settings.py, urls, templates... Important: Don't forget to create the ini...

If you have your data stored in a list and you want to convert this list to a data frame the do.call function is an easy way to achieve this. However, it is important that all list elements have the same length in order to prevent unintended recycling of values. dataList <- list(1:3,4:6,7:9) ...

Ever wanted to call a multicast delegate but you want the entire invokation list to be called even if an exception occurs in any in the chain. Then you are in luck, I have created an extension method that does just that, throwing an AggregateException only after execution of the entire list complete...

To increase the maximum amount of heap memory used Eclipse, edit the eclipse.ini file located in the Eclipse installation directory. This file specifies options for the startup of Eclipse, such as which JVM to use, and the options for the JVM. Specifically, you need to edit the value of the -Xmx JV...

OnClick Listener: @OnClick(R.id.login) public void login(View view) { // Additional logic } All arguments to the listener method are optional: @OnClick(R.id.login) public void login() { // Additional logic } Specific type will be automatically casted: @OnClick(R.id.submit) publi...

Fragments have a different view lifecycle than activities. When binding a fragment in onCreateView, set the views to null in onDestroyView. Butter Knife returns an Unbinder instance when you call bind to do this for you. Call its unbind method in the appropriate lifecycle callback. An example: pub...

Who says you cannot throw multiple exceptions in one method. If you are not used to playing around with AggregateExceptions you may be tempted to create your own data-structure to represent many things going wrong. There are of course were another data-structure that is not an exception would be mor...

You can get list of available commands by following way: >>> python manage.py help If you don't understand any command or looking for optional arguments then you can use -h argument like this >>> python manage.py command_name -h Here command_name will be your desire command...