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![HELLO, PEOPLE!
Let's take it from the command line...
And refactor that into a subroutine...
main(List<String> args) {
String person = "World";
if (args.length > 0) {
person = args[0];
}
print("Hello, $person!");
}
main(List<String> args) {
String person = "World";
if (args.length > 0) {
person = args[0];
}
sayHelloTo(person);
}
sayHelloTo(String aPerson) {
print("Hello, $aPerson!");
}](https://image.slidesharecdn.com/abriefintroductiontodart-150711201459-lva1-app6891/85/A-brief-introduction-to-dart-8-320.jpg)
![LISTS
Also known as arrays or ordered collections
Zerobased indexing (first element is item 0)
In checked mode (during development), can be
optionally typed:
Includes rich set of methods: add, addAll,
indexOf, removeAt, clear, sort and many
more
main () {
var meats = ['cow', 'pig', 'chicken'];
print(meats);
print(meats[0]);
meats.add('turkey');
print(meats[meats.length - 1]);
var only_numbers = <num> [3, 4, 5];
only_numbers.add('duck'); // fails in checked mode
}](https://image.slidesharecdn.com/abriefintroductiontodart-150711201459-lva1-app6891/85/A-brief-introduction-to-dart-13-320.jpg)
![MAPS
Maps have keys and values, both objects
Maps are created with a literal syntax or new Map
Typing information can be added for keys and
values:
main() {
var randal = {
'name': 'Randal L. Schwartz',
'address': '123 Main Street',
'city': 'Portland, Oregon',
};
print(randal['city']);
randal['city'] = 'Beaverton, Oregon';
randal['zip'] = 97001;
}
main() {
var randal = <String,String> {
...](https://image.slidesharecdn.com/abriefintroductiontodart-150711201459-lva1-app6891/85/A-brief-introduction-to-dart-14-320.jpg)
![OPTIONAL ARGS
Required args listed first, followed by optional args
Optional args can be positional or named, but not
both
Optional args can have defaults, or return null
otherwise:
void sayMyName(String first, [String last]) {
if (last != null) {
print("My name is $first $last");
} else {
print("My name is $first");
}
}
void sayMyNameToo(String first, [String last = "Smith"]) {
print("My name is $first $last");
}
main () {
sayMyName("Randal", "Schwartz");
sayMyNameToo("Randal");
}](https://image.slidesharecdn.com/abriefintroductiontodart-150711201459-lva1-app6891/85/A-brief-introduction-to-dart-16-320.jpg)
![CLASS MEMBERS
The dot is used to refer to both methods and
instance variables:
Getters and setters can be defined for instance
variables, allowing transparent migration
Class variables and methods also supported
class Point {
num x;
num y;
String toString() => "Point [$x,$y]";
}
main() {
var point = new Point();
point.x = 4;
point.y = 7;
print(point);
}](https://image.slidesharecdn.com/abriefintroductiontodart-150711201459-lva1-app6891/85/A-brief-introduction-to-dart-21-320.jpg)
![GENERICS
Optional types, so why use generics?
Inform the compiler during checked mode, and
the IDE during development:
Can also be used for interfaces:
main() {
var names = new List<String>();
names.addAll(['Randal', 'Kermit']);
names.add(1e20); // fails because 1e20 is not a String
}
abstract class Cache<T> {
T operator [] (String key);
operator []= (String key, T value);
}](https://image.slidesharecdn.com/abriefintroductiontodart-150711201459-lva1-app6891/85/A-brief-introduction-to-dart-22-320.jpg)
Uploaded byRandal Schwartz
A brief introduction to dart
This document provides an overview of Dart, a modern programming language designed for ease of use and efficient transpilation to JavaScript, suitable for web development including single page applications. It covers Dart's history, key features such as optional typing, built-in libraries, asynchronous operations, and tools for development, as well as examples of basic syntax and functionalities. The document highlights Dart's evolution since its inception at Google and its ecosystem, including libraries and dependency management through 'pub'.
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A brief introduction to dart
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- 7. HELLO, WORLD! Of course... the first code... Let's introduce a variable... That's an untyped variable... let's ensure it's a string... main() { print("Hello, world!"); } main(){ var msg = "Hello, world!"; print(msg); } main() { String person = "World"; print("Hello, $person!"); }
- 8. HELLO, PEOPLE! Let's take it from the command line... And refactor that into a subroutine... main(List<String> args) { Stringperson = "World"; if (args.length > 0) { person = args[0]; } print("Hello, $person!"); } main(List<String> args) { String person = "World"; if (args.length > 0) { person = args[0]; } sayHelloTo(person); } sayHelloTo(String aPerson) { print("Hello, $aPerson!"); }
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- 11. NUMBERS Infinite precision ints in VM, normal range in JavaScript Doubles are classic IEEE 754 standard Converting between strings and numbers: int a =3; int header_constant = 0xBABE; int large = 31415926535897932384626433832795; double pi_like = large / 1e31; main () => print(pi_like); int three = int.parse("3"); double pi_kinda = double.parse("3.14"); String six_string = 6.toString(); String pi_sorta = pi_kinda.toString(); main () => print(pi_sorta);
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- 13. LISTS Also known as arrays or ordered collections Zerobased indexing (first element is item 0) In checked mode (during development), can be optionally typed: Includes rich set of methods: add, addAll, indexOf, removeAt, clear, sort and many more main () { varmeats = ['cow', 'pig', 'chicken']; print(meats); print(meats[0]); meats.add('turkey'); print(meats[meats.length - 1]); var only_numbers = <num> [3, 4, 5]; only_numbers.add('duck'); // fails in checked mode }
- 14. MAPS Maps have keys and values, both objects Maps are created with a literal syntax or new Map Typing information can be added for keys and values: main() { varrandal = { 'name': 'Randal L. Schwartz', 'address': '123 Main Street', 'city': 'Portland, Oregon', }; print(randal['city']); randal['city'] = 'Beaverton, Oregon'; randal['zip'] = 97001; } main() { var randal = <String,String> { ...
- 15. FUNCTIONS Types are optional, but are checked if present and assist IDE: Args can be positional, or named: void sayMyName (StringmyName) { print("My name is $myName."); } sayMyNameToo (myName) => print("My name is $myName."); main () => sayMyName("Randal"); void sayMyName({String first, String last}) { if (last != null) { print("My name is $first $last"); } else { print("My name is $first"); } } main () { sayMyName(first: "Randal"); sayMyName(first: "Randal", last: "Schwartz"); }
- 16. OPTIONAL ARGS Required args listed first, followed by optional args Optional args can be positional or named, but not both Optional args can have defaults, or return null otherwise: void sayMyName(String first,[String last]) { if (last != null) { print("My name is $first $last"); } else { print("My name is $first"); } } void sayMyNameToo(String first, [String last = "Smith"]) { print("My name is $first $last"); } main () { sayMyName("Randal", "Schwartz"); sayMyNameToo("Randal"); }
- 17. OPERATORS Rich set of operators similar to most modern languages 15 levels of precedence, with normal usage of parentheses to override Integer divide: ~/ Pre and post increment and decrement Type testing and casting: is, is! and as Compound assignment: a += 3 Bitwise operators, like & and << Expression if/then/else: var$this = 3 > 4 ? "was true" : "was false"; main () => print($this);
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- 21. CLASS MEMBERS The dot is used to refer to both methods and instance variables: Getters and setters can be defined for instance variables, allowing transparent migration Class variables and methods also supported class Point { numx; num y; String toString() => "Point [$x,$y]"; } main() { var point = new Point(); point.x = 4; point.y = 7; print(point); }
- 22. GENERICS Optional types, so why use generics? Inform the compiler during checked mode, and the IDE during development: Can also be used for interfaces: main() { var names= new List<String>(); names.addAll(['Randal', 'Kermit']); names.add(1e20); // fails because 1e20 is not a String } abstract class Cache<T> { T operator [] (String key); operator []= (String key, T value); }
- 23. ASYNCHRONOUS OPERATIONS Similar to promise libraries in JavaScript Provides Future (one value soon) and Stream (many values over time) interfaces Can use try/catch/finallystyle logic with either of these For simple cases, async can be made to appear nonasync: checkVersion() async { varversion = await lookUpVersion(); if (version == expectedVersion) { // Do something. } else { // Do something else. } }
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