Tutorial by Examples: rom

Given some JSON file "foo.json" like: {"foo": {"bar": {"baz": 1}}} we can call the module directly from the command line (passing the filename as an argument) to pretty-print it: $ python -m json.tool foo.json { "foo": { "bar...

Given a function that accepts a Node-style callback, fooFn(options, function callback(err, result) { ... }); you can promisify it (convert it to a promise-based function) like this: function promiseFooFn(options) { return new Promise((resolve, reject) => fooFn(options, (err, re...

git cherry-pick <commit-hash> will apply the changes made in an existing commit to another branch, while recording a new commit. Essentially, you can copy commits from branch to branch. Given the following tree (Source) dd2e86 - 946992 - 9143a9 - a6fd86 - 5a6057 [master] \ ...

It is tricky to remove items from a list while within a loop, this is due to the fact that the index and length of the list gets changed. Given the following list, here are some examples that will give an unexpected result and some that will give the correct result. List<String> fruits = new...

INSERT INTO Customers (FName, LName, PhoneNumber) SELECT FName, LName, PhoneNumber FROM Employees This example will insert all Employees into the Customers table. Since the two tables have different fields and you don't want to move all the fields over, you need to set which fields to insert int...

main = do line <- getLine putStrLn line Input: This is an example. Output: This is an example.

readFloat :: IO Float readFloat = fmap read getLine main :: IO () main = do putStr "Type the first number: " first <- readFloat putStr "Type the second number: " second <- readFloat putStrLn $ show first ++ " + " ++ show se...

Like in several other parts of the I/O library, functions that implicitly use a standard stream have a counterpart in System.IO that performs the same job, but with an extra parameter at the left, of type Handle, that represents the stream being handled. For instance, getLine :: IO String has a cou...

During a merge, you can pass --ours or --theirs to git checkout to take all changes for a file from one side or the other of a merge. $ git checkout --ours -- file1.txt # Use our version of file1, delete all their changes $ git checkout --theirs -- file2.txt # Use their version of file2, delete ...

Ordinarily, images are pulled automatically from Docker Hub. Docker will attempt to pull any image from Docker Hub that doesn't already exist on the Docker host. For example, using docker run ubuntu when the ubuntu image is not already on the Docker host will cause Docker to initiate a pull of the l...

Syntax: SELECT * FROM table_name Using the asterisk operator * serves as a shortcut for selecting all the columns in the table. All rows will also be selected because this SELECT statement does not have a WHERE clause, to specify any filtering criteria. This would also work the same way if you...

To get info from the requesting url (notice that req is the request object in the handler function of routes). Consider this route definition /settings/:user_id and this particular example /settings/32135?field=name // get the full path req.originalUrl // => /settings/32135?field=name // get...

Many IDEs provide support for generating HTML from Javadocs automatically; some build tools (Maven and Gradle, for example) also have plugins that can handle the HTML creation. However, these tools are not required to generate the Javadoc HTML; this can be done using the command line javadoc tool. ...

Once you have a Dockerfile, you can build an image from it using docker build. The basic form of this command is: docker build -t image-name path If your Dockerfile isn't named Dockerfile, you can use the -f flag to give the name of the Dockerfile to build. docker build -t image-name -f Dockerfi...

The examples below fill in a PhoneNumber for any Employee who is also a Customer and currently does not have a phone number set in the Employees Table. (These examples use the Employees and Customers tables from the Example Databases.) Standard SQL Update using a correlated subquery: UPDATE ...

In classes, super.foo() will look in superclasses only. If you want to call a default implementation from a superinterface, you need to qualify super with the interface name: Fooable.super.foo(). public interface Fooable { default int foo() {return 3;} } public class A extends Object impl...

In case you have reverted back to a past commit and lost a newer commit you can recover the lost commit by running git reflog Then find your lost commit, and reset back to it by doing git reset HEAD --hard <sha1-of-commit>

The getAll() method retrieves all values from the preferences. We can use it, for instance, to log the current content of the SharedPreferences: private static final String PREFS_FILE = "MyPrefs"; public static void logSharedPreferences(final Context context) { SharedPreferences s...

Code first allows you to create your entities (classes) without using a GUI designer or a .edmx file. It is named Code first, because you can create your models first and Entity framework will create database according to mappings for you automatically. Or you can also use this approach with existin...

Few people have issue regarding error message not displaying if existing value is being entered in textbox. So, For Example I'm not allowing user to enter existing email. signup.php (Page where you wanted to sign up new user without existing email id) Remove use yii\bootstrap\ActiveForm; (if p...