Tutorial by Examples: u

A Subject in RxJava is a class that is both an Observable and an Observer. This basically means that it can act as an Observable and pass inputs to subscribers and as an Observer to get inputs from another Observable. Subject<String, String> subject = PublishSubject.create(); subject.subscr...

PublishSubject emits to an Observer only those items that are emitted by the source Observable subsequent to the time of the subscription. A simple PublishSubject example: Observable<Long> clock = Observable.interval(500, TimeUnit.MILLISECONDS); Subject<Long, Long> subjectLong = Publi...

In a multi-project gradle build, you can have a dependency with another module in your build. Example: dependencies { // Dependency on the "mylibrary" module from this project compile project(":mylibrary") } The compile project(':mylibrary') line decla...

Init array of view controllers which will be managed by UIPageViewController. Add a base view controller class which has property identifier which will be used to identify view controllers when working with UIPageViewController data source methods. Let the view controllers to inherit from that bas...

The special symbol T represents the value true in Common Lisp, while the special symbol NIL represents false: CL-USER> (= 3 3) T CL-USER> (= 3 4) NIL They are called “Constant Variables” (sic!) in the standard, since they are variables whose value cannot be modified. As a consequence, y...

R has a number of build in constants. The following constants are available: LETTERS: the 26 upper-case letters of the Roman alphabet letters: the 26 lower-case letters of the Roman alphabet month.abb: the three-letter abbreviations for the English month names month.name: the English names fo...

This quickstart is written for Mac OSX Mavericks, and is a bit more verbose than other installation instructions. It should hopefully cover a few edge cases, such as setting your path, and configuring NPM, which can cause an installation to go awry. # install meteor curl https://install.meteor...

HTML <div id="app"></div> JS document.getElementById('app').innerHTML = '<p>Some text</p>' and now HTML looks like this <div id="app"> <p>Some text</p> </div>

One could easily center a child element using table display property. HTML <div class="wrapper"> <div class="parent"> <div class="child"></div> </div> </div> CSS .wrapper { display: table; vertica...

Cache-Control: private, max-age=60 private specifies that the response can be cached only for user who requested the resource, and can't be reused when other users request the same resource. This is appropriate for responses that depend on cookies.

Cache-Control: no-cache The client will behave as if the response was not cached. This is appropriate for resources that can unpredictably change at any time, and which users must always see in the latest version. Responses with no-cache will be slower (high latency) due to need to contact the s...

Cache-control: no-store Instructs clients no to cache the response in any way, and to forget it at soon as possible. This directive was originally designed for sensitive data (today HTTPS should be used instead), but can be used to avoid polluting caches with responses that can't be reused. It...

Expires — specifies date when the resource becomes stale. It relies on servers and clients having accurate clocks and supporting time zones correctly. Cache-control: max-age takes precedence over Expires, and is generally more reliable. post-check and pre-check directives are non-standard I...

Django handles a request by routing the incoming URL path to a view function. The view function is responsible for returning a response back to the client making the request. Different URLs are usually handled by different view functions. To route the request to a specific view function, Django look...

foldMap maps each element of the Foldable structure to a Monoid, and then combines them into a single value. foldMap and foldr can be defined in terms of one another, which means that instances of Foldable need only give a definition for one of them. class Foldable t where foldMap :: Monoid m...

// Twitter markup documentation: // https://dev.twitter.com/cards/markup String[] twitterTags = { "twitter:site", "twitter:site:id", "twitter:creator", "twitter:creator:id", &q...

For added safety we can define the type of object that the array contains: NSArray<NSString *> *colors = @[@"Red", @"Green", @"Blue", @"Yellow"]; NSMutableArray<NSString *> *myColors = [NSMutableArray arrayWithArray:colors]; [myColors addObject:...

NSArray *myColors = @[@"Red", @"Green", @"Blue", @"Yellow"]; [myColors enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) { NSLog(@"enumerating object %@ at index %lu", obj, idx); }]; By setting the stop parameter to YES you c...

Python provides functions for justifying strings, enabling text padding to make aligning various strings much easier. Below is an example of str.ljust and str.rjust: interstates_lengths = { 5: (1381, 2222), 19: (63, 102), 40: (2555, 4112), 93: (189,305), } for road, length in...

Managing AWS resources that scale up and down runs into the limits of the static inventory host file, that's why we need something dynamic. And that's what the dynamic inventories are for. Let's start: Download these ec2.ini and ec2.py files to the your project folder: cd my_ansible_project wget...