Tutorial by Examples: d

This example uses the Dropbox .NET library to try to get the metadata for an item at a particular path, and checks for a NotFound error: try { var metadata = await this.client.Files.GetMetadataAsync("/non-existant path"); Console.WriteLine(metadata.Name); } catch (Dropbox.Api.A...

Method injection is a fine grained way of injecting dependencies into processing. Consider a method that does some processing based on the current date. The current date is hard to change from a test, so it is much easier to pass a date into the method that you want to test. public void ProcessRe...

Whilst extracting dependencies out of your code so that they can be injected makes your code easier to test, it pushes the problem further up the hierarchy and can also result in objects that are difficult to construct. Various dependency injection frameworks / Inversion of Control Containers have ...

Commits can be squashed during a git rebase. It is recommended that you understand rebasing before attempting to squash commits in this fashion. Determine which commit you would like to rebase from, and note its commit hash. Run git rebase -i [commit hash]. Alternatively, you can type HE...

This program, saved to a file named HelloWorld.dpr, compiles to a console application that prints "Hello World" to the console: program HelloWorld; {$APPTYPE CONSOLE} begin WriteLn('Hello World'); end.

C++14 Lambdas can capture expressions, rather than just variables. This permits lambdas to store move-only types: auto p = std::make_unique<T>(...); auto lamb = [p = std::move(p)]() //Overrides capture-by-value of `p`. { p->SomeFunc(); }; This moves the outer p variable into th...

By default, local variables that are not explicitly specified in the capture list, cannot be accessed from within the lambda body. However, it is possible to implicitly capture variables named by the lambda body: int a = 1; int b = 2; // Default capture by value [=]() { return a + b; }; // OK;...

Dim input as String = Console.ReadLine() Console.ReadLine() will read the console input from the user, up until the next newline is detected (usually upon pressing the Enter or Return key). Code execution is paused in the current thread until a newline is provided. Afterwards, the next line of co...

Libraries other than jQuery may also use $ as an alias. This can cause interference between those libraries and jQuery. To release $ for use with other libraries: jQuery.noConflict(); After calling this function, $ is no longer an alias for jQuery. However, you can still use the variable jQuery...

Create a snapshot of a whole database: mysqldump [options] db_name > filename.sql Create a snapshot of multiple databases: mysqldump [options] --databases db_name1 db_name2 ... > filename.sql mysqldump [options] --all-databases > filename.sql Create a snapshot of one or more tables...

> mysqldump -u username -p [other options] Enter password: If you need to specify the password on the command line (e.g. in a script), you can add it after the -p option without a space: > mysqldump -u username -ppassword [other options] If you password contains spaces or special chara...

mysql [options] db_name < filename.sql Note that: db_name needs to be an existing database; your authenticated user has sufficient privileges to execute all the commands inside your filename.sql; The file extension .sql is fully a matter of style. Any extension would work. You cannot spe...

c++14 Lambda functions can take arguments of arbitrary types. This allows a lambda to be more generic: auto twice = [](auto x){ return x+x; }; int i = twice(2); // i == 4 std::string s = twice("hello"); // s == "hellohello" This is implemented in C++ by making the closur...

To authenticate to Watson services, you need credentials for each service that you plan to use. Depending on the service, you will need to pass a username and password with Basic Authentication, or you will need to pass an API key in a parameter for each request you make. How to get credentials for...

For any file operations, you will need the filesystem module: const fs = require('fs'); Reading a String fs.readFileSync behaves similarly to fs.readFile, but does not take a callback as it completes synchronously and therefore blocks the main thread. Most node.js developers prefer the asynch...

In this tutorial we're going to learn how to set up the PayPal Android SDK to process a simple payment via either a PayPal payment or a credit card purchase. At the end of this example, you should have a simple button in an application that, when clicked, will forward the user to PayPal to confirm a...

C++11 A std::unique_ptr is a class template that manages the lifetime of a dynamically stored object. Unlike for std::shared_ptr, the dynamic object is owned by only one instance of a std::unique_ptr at any time, // Creates a dynamic int with value of 20 owned by a unique pointer std::unique_pt...

If you need to create a JSONObject and put data in it, consider the following example: // Create a new javax.json.JSONObject instance. JSONObject first = new JSONObject(); first.put("foo", "bar"); first.put("temperature", 21.5); first.put("year", 2016);...

If you need to get data from a JSONObject, consider the following example: String json = "{\"foo\":\"bar\",\"temperature\":21.5,\"year\":2016,\"message\":{\"Hello\":\"world\"},\"months\":[\"January\",\&qu...

JSONObject and JSONArray have a few methods that are very useful while dealing with a possibility that a value your are trying to get does not exist or is of another type. JSONObject obj = new JSONObject(); obj.putString("foo", "bar"); // For existing properties of the corre...