Tutorial by Examples: r

virtualenv is a tool to build isolated Python environments. This program creates a folder which contains all the necessary executables to use the packages that a Python project would need. Installing the virtualenv tool This is only required once. The virtualenv program may be available through yo...

Normally you would want to avoid using cursors as they can have negative impacts on performance. However in some special cases you may need to loop through your data record by record and perform some action. DECLARE @orderId AS INT -- here we are creating our cursor, as a local cursor and only a...

public class DatabaseHelper extends SQLiteOpenHelper { private static final String DATABASE_NAME = "Example.db"; private static final int DATABASE_VERSION = 3; // For all Primary Keys _id should be used as column name public static final String COLUMN_ID = "_id&q...

// You need a writable database to insert data final SQLiteDatabase database = openHelper.getWritableDatabase(); // Create a ContentValues instance which contains the data for each column // You do not need to specify a value for the PRIMARY KEY column. // Unique values for these are automatic...

A struct can be used to bundle multiple return values: C++11 struct foo_return_type { int add; int sub; int mul; int div; }; foo_return_type foo(int a, int b) { return {a + b, a - b, a * b, a / b}; } auto calc = foo(5, 12); C++11 Instead of assignment to indi...

If you've got a session which you wish to destroy, you can do this with session_destroy() /* Let us assume that our session looks like this: Array([firstname] => Jon, [id] => 123) We first need to start our session: */ session_start(); /* We can now remove all the v...

Just execute lsb_release -a. On Debian: $ lsb_release -a No LSB modules are available. Distributor ID: Debian Description: Debian GNU/Linux testing (stretch) Release: testing Codename: stretch On Ubuntu: $ lsb_release -a No LSB modules are available. Distributor ID: Ubun...

The most common way to create a Symbol object is by prefixing the string identifier with a colon: :a_symbol # => :a_symbol :a_symbol.class # => Symbol Here are some alternative ways to define a Symbol, in combination with a String literal: :"a_symbol" "a_symbol&quot...

Given a String: s = "something" there are several ways to convert it to a Symbol: s.to_sym # => :something :"#{s}" # => :something

Given a Symbol: s = :something The simplest way to convert it to a String is by using the Symbol#to_s method: s.to_s # => "something" Another way to do it is by using the Symbol#id2name method which is an alias for the Symbol#to_s method. But it's a method that is unique to the...

UIAlertView and UIActionSheet are Deprecated in iOS 8 and Later. So Apple introduced a new controller for AlertView and ActionSheet called UIAlertController , changing the preferredStyle, you can switch between AlertView and ActionSheet. There is no delegate method for it because all button events a...

NSDictionary *inventory = @{ @"Mercedes-Benz SLK250" : @(13), @"BMW M3 Coupe" : @(self.BMWM3CoupeInventory.count), @"Last Updated" : @"Jul 21, 2016", @"Next Update" : self.nextInventoryUpdateString };

NSDictionary *inventory = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithInt:13], @"Mercedes-Benz SLK250", [NSNumber numberWithInt:22], @"Mercedes-Benz E350", [NSNumber numberWithInt:19], @"BMW M3 Coupe", [NSNumber numberWithInt:16],...

To combine an NSArray of NSString into a new NSString: NSArray *yourWords = @[@"Objective-C", @"is", @"just", @"awesome"]; NSString *sentence = [yourWords componentsJoinedByString:@" "]; // Sentence is now: @"Objective-C is just awesome&quo...

If a code module does not contain Option Explicit at the top of the module, then the compiler will automatically (that is, "implicitly") create variables for you when you use them. They will default to variable type Variant. Public Sub ExampleDeclaration() someVariable = 10 ...

Scope A variable can be declared (in increasing visibility level): At procedure level, using the Dim keyword in any procedure; a local variable. At module level, using the Private keyword in any type of module; a private field. At instance level, using the Friend keyword in any type of class m...

The Dim statement should be reserved for local variables. At module-level, prefer explicit access modifiers: Private for private fields, which can only be accessed within the module they're declared in. Public for public fields and global variables, which can be accessed by any calling code. Fr...

You can open the VB editor in any of the Microsoft Office applications by pressing Alt+F11 or going to the Developer tab and clicking on the "Visual Basic" button. If you don't see the Developer tab in the Ribbon, check if this is enabled. By default the Developer tab is disabled. To enab...

To begin using WebDriver you will need to obtain the relevant Driver from the Selenium site: Selenium HQ Downloads. From here you need to download the driver relevant to the browser(s) and/or platform(s) you are trying to run WebDriver on, e.g. if you were testing in Chrome the Selenium site will di...

Rails provides several ways to organize your routes. Scope by URL: scope 'admin' do get 'dashboard', to: 'administration#dashboard' resources 'employees' end This generates the following routes get '/admin/dashboard', to: 'administration#dashboard' post '/admin/empl...