Tutorial by Examples: er

The syntax for Java generics bounded wildcards, representing the unknown type by ? is: ? extends T represents an upper bounded wildcard. The unknown type represents a type that must be a subtype of T, or type T itself. ? super T represents a lower bounded wildcard. The unknown type repres...

For the following DataFrame: import numpy as np import pandas as pd np.random.seed(0) df = pd.DataFrame({'Age': np.random.randint(20, 70, 100), 'Sex': np.random.choice(['Male', 'Female'], 100), 'number_of_foo': np.random.randint(1, 20, 100)}) df.head() ...

The prototype pattern focuses on creating an object that can be used as a blueprint for other objects through prototypal inheritance. This pattern is inherently easy to work with in JavaScript because of the native support for prototypal inheritance in JS which means we don't need to spend time or e...

Alamofire.request(.GET, "https://httpbin.org/get", parameters: ["foo": "bar"]) .validate() .response { request, response, data, error in print(request) print(response) print(data) print(error) }

Alamofire.request(.GET, "https://httpbin.org/get") .validate() .responseString { response in print("Response String: \(response.result.value)") } .responseJSON { response in print("Response JSON: \(response.result.value)") ...

public string Remove() { string input = "Hello./!"; return Regex.Replace(input, "[^a-zA-Z0-9]", ""); }

Extension methods can be used for writing strongly typed wrappers for dictionary-like objects. For example a cache, HttpContext.Items at cetera... public static class CacheExtensions { public static void SetUserInfo(this Cache cache, UserInfo data) => cache["UserInfo"] ...

This is a runtime error that happens when you request a large amount of memory on the heap. This is common when loading a Bitmap into an ImageView. You have some options: Use a large application heap Add the "largeHeap" option to the application tag in your AndroidManifest.xml. This...

Often when programming it is necessary to make some distinction between a variable that has a value and one that does not. For reference types, such as C Pointers, a special value such as null can be used to indicate that the variable has no value. For intrinsic types, such as an integer, it is mo...

In Swift, structures use a simple “dot syntax” to access their members. For example: struct DeliveryRange { var range: Double let center: Location } let storeLocation = Location(latitude: 44.9871, longitude: -93.2758) var pizzaRange = DeliveryRange(range: 200...

You can also receive regular updates of the user's location; for example, as they move around while using a mobile device. Location tracking over time can be very sensitive, so be sure to explain to the user ahead of time why you're requesting this permission and how you'll use the data. if (naviga...

Sometimes, programmers who are new Java will use primitive types and wrappers interchangeably. This can lead to problems. Consider this example: public class MyRecord { public int a, b; public Integer c, d; } ... MyRecord record = new MyRecord(); record.a = 1; // OK ...

It is possible to define custom string interpolators in addition to the built-in ones. my"foo${bar}baz" Is expanded by the compiler to: new scala.StringContext("foo", "baz").my(bar) scala.StringContext has no my method, therefore it can be provided by implicit c...

If you want to parse a String to enum with Gson: {"status" : "open"} public enum Status { @SerializedName("open") OPEN, @SerializedName("waiting") WAITING, @SerializedName("confirm") CONFIRM, @SerializedName(&...

Caller info attributes can be used to pass down information about the invoker to the invoked method. The declaration looks like this: using System.Runtime.CompilerServices; public void LogException(Exception ex, [CallerMemberName]string callerMemberName = "", ...

Optional Parameters In TypeScript, every parameter is assumed to be required by the function. You can add a ? at the end of a parameter name to set it as optional. For example, the lastName parameter of this function is optional: function buildName(firstName: string, lastName?: string) { // ...

Returns one of two values depending on the value of a Boolean expression. Syntax: condition ? expression_if_true : expression_if_false; Example: string name = "Frank"; Console.WriteLine(name == "Frank" ? "The name is Frank" : "The name is not Frank"); ...

Boolean(...) will convert any data type into either true or false. Boolean("true") === true Boolean("false") === true Boolean(-1) === true Boolean(1) === true Boolean(0) === false Boolean("") === false Boolean("1") === true Boolean("0") === t...

In themes.xml: <style name="MyActivityTheme" parent="Theme.AppCompat"> <!-- Theme attributes here --> </style> In AndroidManifest.xml: <application android:icon="@mipmap/ic_launcher" android:label="@string/app_name" ...

Pointer Methods Pointer methods can be called even if the variable is itself not a pointer. According to the Go Spec, . . . a reference to a non-interface method with a pointer receiver using an addressable value will automatically take the address of that value: t.Mp is equivalent to (&t)....