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I am very new to Dart so excuse me if I didnt see this part.
I want to make a union type e.g. for a function input. In TS this would be:
let variableInput: string | number
typedef doesnt really define types but functions and enums dont really help too.
On the other side how should it look like when a function return either one or the other of two types? There must be something I dont see here.
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No, you don't have two return types. It's a generic method you are seeing.
How can a variable have 2 data types? It cannot. An object has one type. A single type can represent values of different types (unions, std::variant ).
You can return multiple values from a function using either a dictionary, a tuple, or a list. These data types all let you store multiple values.
To allow a function to return multiple data types, you simply add a pipe after a data type. Related articles: I like to tweet about TypeScript and post helpful code snippets. Follow me there if you would like some too!
Use a union type to define a function with multiple return types in TypeScript, e.g. function getValue (num: number): string | number {}. The function must return a value that is represented in the union type, otherwise the type checker throws an error. Copied! We used a union type to set the return type of a function with multiple return types.
A Generic class can have muliple type parameters. Following example will showcase above mentioned concept. Create the following java program using any editor of your choice. GenericsTester.java
We can use following solutions to return multiple values. We can return an array in Java. Below is a Java program to demonstrate the same. We can use Pair in Java to return two values. We can encapsulate all returned types into a class and then return an object of that class. Let us have a look at the following code.
If returned elements are of different types. Using Pair (If there are only two returned values) We can use Pair in Java to return two values. import javafx.util.Pair; class GfG {. public static Pair<Integer, String> getTwo () {. return new Pair<Integer, String> (10, "GeeksforGeeks"); }
There are no union types in Dart.
The way to do this in Dart is returning/accepting dynamic as a type:
dynamic stringOrNumber() { ... }
void main() {
final value = stringOrNumber();
if (value is String) {
// Handle a string value.
} else if (value is num) {
// Handle a number.
} else {
throw ArgumentError.value(value);
}
}
See also: https://dart.dev/guides/language/sound-dart
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