Tutorial by Examples: g

Suppose you have many changes in one or more files but from each file you only want to commit some of the changes, you can select the desired changes using: git add -p or git add -p [file] Each of your changes will be displayed individually, and for each change you will be prompted to choose...

A simple context tree (containing some common values that might be request scoped and included in a context) built from Go code like the following: // Pseudo-Go ctx := context.WithValue( context.WithDeadline( context.WithValue(context.Background(), sidKey, sid), time.Now().A...

First, ensure you have imported sessions from flask from flask import session To use session, a Flask application needs a defined SECRET_KEY. app = Flask(__name__) app.secret_key = 'app secret key' Sessions are implemented by default using a cookie signed with the secret key. This ensures t...

NSArray *myColors = @[@"Red", @"Green", @"Blue", @"Yellow"]; // Fast enumeration // myColors cannot be modified inside the loop for (NSString *color in myColors) { NSLog(@"Element %@", color); } // Using indices for (NSUInteger i = 0; ...

With automatic reference counting (ARC), the compiler inserts retain, release, and autorelease statements where they are needed, so you don't have to write them yourself. It also writes dealloc methods for you. The sample program from Manual Memory Management looks like this with ARC: @interface M...

Modern A weak reference looks like one of these: @property (weak) NSString *property; NSString *__weak variable; If you have a weak reference to an object, then under the hood: You're not retaining it. When it gets deallocated, every reference to it will automatically be set to nil Obje...

This is an example of a program written with manual memory management. You really shouldn't write your code like this, unless for some reason you can't use ARC (like if you need to support 32-bit). The example avoids @property notation to illustrate how you used to have to write getters and setters....

A word of caution: AsyncTask has many gotcha's apart from the memory leak described here. So be careful with this API, or avoid it altogether if you don't fully understand the implications. There are many alternatives (Thread, EventBus, RxAndroid, etc). One common mistake with AsyncTask is to c...

The isEqual: method is the only reliable way to determine whether two images contain the same image data. The image objects you create may be different from each other, even when you initialize them with the same cached image data. The only way to determine their equality is to use the isEqual...

Assuming that you have successfully created a JFrame and that Swing has been imported... You can import Swing entirely import javax.Swing.*; or You can import the Swing Components/Frame that you intend to use import javax.Swing.Jframe; import javax.Swing.JButton; Now down to adding the J...

Leaflet is an open-source JavaScript library for making dynamic maps for the web. RStudio wrote R bindings for Leaflet, available through its leaflet package, built with htmlwidgets. Leaflet maps integrate well with the RMarkdown and Shiny ecosystems. The interface is piped, using a leaflet() funct...

PHP is a loosely typed language. This means that, by default, it doesn't require operands in an expression to be of the same (or compatible) types. For example, you can append a number to a string and expect it to work. var_dump ("This is example number " . 1); The output will be: ...

When reading from a file, we want to be able to know when we've reached the end of that file. Knowing that fgets() returns false at the end of the file, we might use this as the condition for a loop. However, if the data returned from the last read happens to be something that evaluates as boolean f...

Add the following dependency to the build.gradle file: compile 'com.nostra13.universalimageloader:universal-image-loader:1.9.5' Add the following permissions to the AndroidManifest.xml file: <uses-permission android:name="android.permission.INTERNET" /> <uses-permiss...

Load an image, decode it into a bitmap, and display the bitmap in an ImageView (or any other view which implements the ImageAware interface): ImageLoader.getInstance().displayImage(imageUri, imageView); Load an image, decode it into a bitmap, and return the bitmap to a callback: ImageLo...

To change MySQL's root user password: Step 1: Stop the MySQL server. in Ubuntu or Debian: sudo /etc/init.d/mysql stop in CentOS, Fedora or Red Hat Enterprise Linux: sudo /etc/init.d/mysqld stop Step 2: Start the MySQL server without the privilege system. sudo mysqld_safe --skip-grant-tab...

Using the Story Board: Select the tab bar item from the corresponding view controller and go to the attributes inspector If you want a built-in icon and title, set the 'System Item' to the corresponding value. For a custom icon, add the required images to the assets folder and set the 'System It...

If you need an ActiveRecord method to raise an exception instead of a false value in case of failure, you can add ! to them. This is very important. As some exceptions/failures are hard to catch if you don't use ! on them. I recommended doing this in your development cycle to write all your ActiveRe...

for loop: arr=(a b c d e f) for i in "${arr[@]}";do echo "$i" done Or for ((i=0;i<${#arr[@]};i++));do echo "${arr[$i]}" done while loop: i=0 while [ $i -lt ${#arr[@]} ];do echo "${arr[$i]}" i=$(expr $i + 1) done Or i=0...

It is very rare that you'll ever want to use Select or Activate in your code, but some Excel methods do require a worksheet or workbook to be activated before they'll work as expected. If you're just starting to learn VBA, you'll often be suggested to record your actions using the macro recorder, t...