Tutorial by Examples: d

WebRTC is an open framework for the web that enables Real Time Communications in the browser. It includes the fundamental building blocks for high-quality communications on the web, such as network, audio and video components used in voice and video chat applications. These components, when impleme...

This is an example on how to use React Native's BackAndroid along with the Navigator. componentWillMount registers an event listener to handle the taps on the back button. It checks if there is another view in the history stack, and if there is one, it goes back -otherwise it keeps the default beha...

You can start the remote debugging from Developer menu. After selecting the enable remote debugging it will open Google Chrome, So that you can log the output into your console. You can also write debugger syntax into your js code.

Polymorphism without inheritance in the form of duck typing as available in Python due to its dynamic typing system. This means that as long as the classes contain the same methods the Python interpreter does not distinguish between them, as the only checking of the calls occurs at run-time. class ...

SELECT * INTO NewTable FROM OldTable Creates a new table with structure of old table and inserts all rows into the new table. Some Restrictions You cannot specify a table variable or table-valued parameter as the new table. You cannot use SELECT…INTO to create a partitioned table, even whe...

This is something that can be frustrating: you make a visualisation using D3.js but the rectangle you want on top is hidden behind another rectangle, or the line you planned to be behind some circle is actually over it. You try to solve this using the z-index in your CSS, but it doesn't work (in SVG...

adb shell am start -n com.android.settings/.DevelopmentSettings Will navigate your device/emulator to the Developer Options section.

This is relevant for apps that implement a BootListener. Test your app by killing your app and then test with: adb shell am broadcast -a android.intent.action.BOOT_COMPLETED -c android.intent.category.HOME -n your.app/your.app.BootListener (replace your.package/your.app.BootListener with proper ...

First define an ExitActivity in the AndroidManifest.xml <activity android:name="com.your_example_app.activities.ExitActivity" android:autoRemoveFromRecents="true" android:theme="@android:style/Theme.NoDisplay" /> Afterwards the ExitA...

When we are working on a framework, if the constraints are not too complex, we'd better use Interface Builder or NSLayoutConstraint in code to make it smaller enough, instead of import Masonry or SnapKit. for example: Objective-C // 1. create views UIView *blueView = [[UIView alloc...

std::function type erases down to a few operations. One of the things it requires is that the stored value be copyable. This causes problems in a few contexts, like lambdas storing unique ptrs. If you are using the std::function in a context where copying doesn't matter, like a thread pool where ...

When factors are created with defaults, levels are formed by as.character applied to the inputs and are ordered alphabetically. charvar <- rep(c("W", "n", "c"), times=c(17,20,14)) f <- factor(charvar) levels(f) # [1] "c" "n" "W" ...

To normalize the database in the second form, there must not be any partial dependency of any column on primary key. Let's consider the following example: idnamedobsubject1Mark1-1-1981Physics2Jack2-2-1982Math2Jack2-2-1982Biology3John3-3-1983Math This table is considered to have a composite primar...

For more advanced regex operations it's best to use CL_ABAP_REGEX and its related classes. DATA: lv_test TYPE string, lo_regex TYPE REF TO cl_abap_regex. lv_test = 'The quick brown fox'. CREATE OBJECT lo_regex EXPORTING pattern = 'q(...)\w'. DATA(lo_matcher) = lo_regex->cr...

SQL Server 2008 R2 SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED This is the most permissive isolation level, in that it does not cause any locks at all. It specifies that statements can read all rows, including rows that have been written in transactions but not yet committed (i.e., they are...

To preload remote images and ensure that the image is only downloaded once: Glide.with(context) .load(yourUrl) .diskCacheStrategy(DiskCacheStrategy.SOURCE) .preload(); Then: Glide.with(context) .load(yourUrl) .diskCacheStrategy(DiskCacheStrategy.SOURCE) // ALL works her...

The first mistake that nearly every single programmer makes is presuming that this code will work as intended: float total = 0; for(float a = 0; a != 2; a += 0.01f) { total += a; } The novice programmer assumes that this will sum up every single number in the range 0, 0.01, 0.02, 0.03, .....

Collections and Maps evaluates to true if not null and not empty and false if null or empty /* an empty map example*/ def userInfo = [:] if (!userInfo) userInfo << ['user': 'Groot', 'species' : 'unknown' ] will add user: 'Groot' , species : 'unknown' as default userInfo since the u...

Sometimes it may be useful to have a specific asBoolean definition in your own program for some kind of objects. /** an oversimplified robot controller */ class RunController { def complexCondition int position = 0 def asBoolean() { return complexCondition(this...

Not all type erasure involves virtual inheritance, allocations, placement new, or even function pointers. What makes type erasure type erasure is that it describes a (set of) behavior(s), and takes any type that supports that behavior and wraps it up. All information that isn't in that set of beha...