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@ -3,27 +3,28 @@ language: dart
filename: learndart.dart
contributors:
- ["Joao Pedrosa", "https://github.com/jpedrosa/"]
- ["Vince Ramces Oliveros", "https://github.com/ram231"]
---
Dart is a newcomer into the realm of programming languages.
It borrows a lot from other mainstream languages, having as a goal not to deviate too much from
its JavaScript sibling. Like JavaScript, Dart aims for great browser integration.
~~its JavaScript sibling. Like JavaScript, Dart aims for great browser integration.~~
Dart's most controversial feature must be its Optional Typing.
Dart's most controversial feature must be its ~~Optional Typing~~ Static Type safety and [Sound Type checks](https://dart.dev/guides/language/sound-dart).
```dart
import "dart:collection";
import "dart:math" as DM;
import "dart:math" as math;
// Welcome to Learn Dart in 15 minutes. http://www.dartlang.org/
// This is an executable tutorial. You can run it with Dart or on
// the Try Dart! site if you copy/paste it there. http://try.dartlang.org/
// Function declaration and method declaration look the same. Function
// declarations can be nested. The declaration takes the form of
// name() {} or name() => singleLineExpression;
// The fat arrow function declaration has an implicit return for the result of
// the expression.
/// Welcome to Learn Dart in 15 minutes. http://dart.dev/
/// This is an executable tutorial. You can run it with Dart or on
/// the Try Dart! site if you copy/paste it there. http://dartpad.dev/
/// You can also run Flutter in DartPad by click the `< > New Pad ` and choose Flutter
/// Function declaration and method declaration look the same. Function
/// declarations can be nested. The declaration takes the form of
/// name() {} or name() => singleLineExpression;
/// The fat arrow function declaration can be an implicit or explicit return for the result of
/// the expression.
example1() {
nested1() {
nested2() => print("Example1 nested 1 nested 2");
@ -32,29 +33,30 @@ example1() {
nested1();
}
// Anonymous functions don't include a name.
/// Anonymous functions don't include a name.
example2() {
nested1(fn) {
//// Explicit return type.
nested1(Function<void> fn) {
fn();
}
nested1(() => print("Example2 nested 1"));
}
// When a function parameter is declared, the declaration can include the
// number of parameters the function takes by specifying the names of the
// parameters it takes.
/// When a function parameter is declared, the declaration can include the
/// number of parameters the function takes by specifying the names of the
/// parameters it takes.
example3() {
planA(fn(informSomething)) {
fn("Example3 plan A");
}
planB(fn) { // Or don't declare number of parameters.
planB(fn) { /// Or don't declare number of parameters.
fn("Example3 plan B");
}
planA((s) => print(s));
planB((s) => print(s));
}
// Functions have closure access to outer variables.
/// Functions have closure access to outer variables.
var example4Something = "Example4 nested 1";
example4() {
nested1(fn(informSomething)) {
@ -63,8 +65,8 @@ example4() {
nested1((s) => print(s));
}
// Class declaration with a sayIt method, which also has closure access
// to the outer variable as though it were a function as seen before.
/// Class declaration with a sayIt method, which also has closure access
/// to the outer variable as though it were a function as seen before.
var example5method = "Example5 sayIt";
class Example5Class {
sayIt() {
@ -72,14 +74,14 @@ class Example5Class {
}
}
example5() {
// Create an anonymous instance of the Example5Class and call the sayIt
// method on it.
/// Create an anonymous instance of the Example5Class and call the sayIt
/// method on it.
new Example5Class().sayIt();
}
// Class declaration takes the form of class name { [classBody] }.
// Where classBody can include instance methods and variables, but also
// class methods and variables.
/// Class declaration takes the form of class name { [classBody] }.
/// Where classBody can include instance methods and variables, but also
/// class methods and variables.
class Example6Class {
var instanceVariable = "Example6 instance variable";
sayIt() {
@ -90,7 +92,7 @@ example6() {
new Example6Class().sayIt();
}
// Class methods and variables are declared with "static" terms.
/// Class methods and variables are declared with "static" terms.
class Example7Class {
static var classVariable = "Example7 class variable";
static sayItFromClass() {
@ -105,11 +107,11 @@ example7() {
new Example7Class().sayItFromInstance();
}
// Literals are great, but there's a restriction for what literals can be
// outside of function/method bodies. Literals on the outer scope of class
// or outside of class have to be constant. Strings and numbers are constant
// by default. But arrays and maps are not. They can be made constant by
// declaring them "const".
/// Literals are great, but there's a restriction for what literals can be
/// outside of function/method bodies. Literals on the outer scope of class
/// or outside of class have to be constant. Strings and numbers are constant
/// by default. But arrays and maps are not. They can be made constant by
/// declaring them "const".
var example8Array = const ["Example8 const array"],
example8Map = const {"someKey": "Example8 const map"};
example8() {
@ -117,9 +119,9 @@ example8() {
print(example8Map["someKey"]);
}
// Loops in Dart take the form of standard for () {} or while () {} loops,
// slightly more modern for (.. in ..) {}, or functional callbacks with many
// supported features, starting with forEach.
/// Loops in Dart take the form of standard for () {} or while () {} loops,
/// slightly more modern for (.. in ..) {}, or functional callbacks with many
/// supported features, starting with forEach.
var example9Array = const ["a", "b"];
example9() {
for (var i = 0; i < example9Array.length; i++) {
@ -136,7 +138,7 @@ example9() {
example9Array.forEach((e) => print("Example9 forEach loop '${e}'"));
}
// To loop over the characters of a string or to extract a substring.
/// To loop over the characters of a string or to extract a substring.
var example10String = "ab";
example10() {
for (var i = 0; i < example10String.length; i++) {
@ -147,14 +149,14 @@ example10() {
}
}
// Int and double are the two supported number formats.
/// Int and double are the two supported number formats.
example11() {
var i = 1 + 320, d = 3.2 + 0.01;
print("Example11 int ${i}");
print("Example11 double ${d}");
}
// DateTime provides date/time arithmetic.
/// DateTime provides date/time arithmetic.
example12() {
var now = new DateTime.now();
print("Example12 now '${now}'");
@ -162,7 +164,7 @@ example12() {
print("Example12 tomorrow '${now}'");
}
// Regular expressions are supported.
/// Regular expressions are supported.
example13() {
var s1 = "some string", s2 = "some", re = new RegExp("^s.+?g\$");
match(s) {
@ -176,7 +178,7 @@ example13() {
match(s2);
}
// Boolean expressions support implicit conversions and dynamic type
/// Boolean expressions support implicit conversions and dynamic type
example14() {
var a = true;
if (a) {
@ -186,11 +188,11 @@ example14() {
if (a) {
print("true, a is $a");
} else {
print("false, a is $a"); // runs here
print("false, a is $a"); /// runs here
}
// dynamic typed null can be convert to bool
var b;// b is dynamic type
/// dynamic typed null can be convert to bool
var b;/// b is dynamic type
b = "abc";
try {
if (b) {
@ -199,35 +201,35 @@ example14() {
print("false, b is $b");
}
} catch (e) {
print("error, b is $b"); // this could be run but got error
print("error, b is $b"); /// this could be run but got error
}
b = null;
if (b) {
print("true, b is $b");
} else {
print("false, b is $b"); // runs here
print("false, b is $b"); /// runs here
}
// statically typed null can not be convert to bool
/// statically typed null can not be convert to bool
var c = "abc";
c = null;
// complie failed
// if (c) {
// print("true, c is $c");
// } else {
// print("false, c is $c");
// }
/// complie failed
/// if (c) {
/// print("true, c is $c");
/// } else {
/// print("false, c is $c");
/// }
}
// try/catch/finally and throw are used for exception handling.
// throw takes any object as parameter;
/// try/catch/finally and throw are used for exception handling.
/// throw takes any object as parameter;
example15() {
try {
try {
throw "Some unexpected error.";
} catch (e) {
print("Example15 an exception: '${e}'");
throw e; // Re-throw
throw e; /// Re-throw
}
} catch (e) {
print("Example15 catch exception being re-thrown: '${e}'");
@ -236,8 +238,8 @@ example15() {
}
}
// To be efficient when creating a long string dynamically, use
// StringBuffer. Or you could join a string array.
/// To be efficient when creating a long string dynamically, use
/// StringBuffer. Or you could join a string array.
example16() {
var sb = new StringBuffer(), a = ["a", "b", "c", "d"], e;
for (e in a) { sb.write(e); }
@ -246,8 +248,8 @@ example16() {
print("Example16 join string array '${a.join()}'");
}
// Strings can be concatenated by just having string literals next to
// one another with no further operator needed.
/// Strings can be concatenated by just having string literals next to
/// one another with no further operator needed.
example17() {
print("Example17 "
"concatenate "
@ -255,44 +257,44 @@ example17() {
"just like that");
}
// Strings have single-quote or double-quote for delimiters with no
// actual difference between the two. The given flexibility can be good
// to avoid the need to escape content that matches the delimiter being
// used. For example, double-quotes of HTML attributes if the string
// contains HTML content.
/// Strings have single-quote or double-quote for delimiters with no
/// actual difference between the two. The given flexibility can be good
/// to avoid the need to escape content that matches the delimiter being
/// used. For example, double-quotes of HTML attributes if the string
/// contains HTML content.
example18() {
print('Example18 <a href="etc">'
"Don't can't I'm Etc"
'</a>');
}
// Strings with triple single-quotes or triple double-quotes span
// multiple lines and include line delimiters.
/// Strings with triple single-quotes or triple double-quotes span
/// multiple lines and include line delimiters.
example19() {
print('''Example19 <a href="etc">
Example19 Don't can't I'm Etc
Example19 </a>''');
}
// Strings have the nice interpolation feature with the $ character.
// With $ { [expression] }, the return of the expression is interpolated.
// $ followed by a variable name interpolates the content of that variable.
// $ can be escaped like so \$ to just add it to the string instead.
/// Strings have the nice interpolation feature with the $ character.
/// With $ { [expression] }, the return of the expression is interpolated.
/// $ followed by a variable name interpolates the content of that variable.
/// $ can be escaped like so \$ to just add it to the string instead.
example20() {
var s1 = "'\${s}'", s2 = "'\$s'";
print("Example20 \$ interpolation ${s1} or $s2 works.");
}
// Optional types allow for the annotation of APIs and come to the aid of
// IDEs so the IDEs can better refactor, auto-complete and check for
// errors. So far we haven't declared any types and the programs have
// worked just fine. In fact, types are disregarded during runtime.
// Types can even be wrong and the program will still be given the
// benefit of the doubt and be run as though the types didn't matter.
// There's a runtime parameter that checks for type errors which is
// the checked mode, which is said to be useful during development time,
// but which is also slower because of the extra checking and is thus
// avoided during deployment runtime.
/// Optional types allow for the annotation of APIs and come to the aid of
/// IDEs so the IDEs can better refactor, auto-complete and check for
/// errors. So far we haven't declared any types and the programs have
/// worked just fine. In fact, types are disregarded during runtime.
/// Types can even be wrong and the program will still be given the
/// benefit of the doubt and be run as though the types didn't matter.
/// There's a runtime parameter that checks for type errors which is
/// the checked mode, which is said to be useful during development time,
/// but which is also slower because of the extra checking and is thus
/// avoided during deployment runtime.
class Example21 {
List<String> _names;
Example21() {
@ -315,7 +317,7 @@ void example21() {
print("Example21 names '${o.names}' and length '${o.length}'");
}
// Class inheritance takes the form of class name extends AnotherClassName {}.
/// Class inheritance takes the form of class name extends AnotherClassName {}.
class Example22A {
var _name = "Some Name!";
get name => _name;
@ -326,13 +328,13 @@ example22() {
print("Example22 class inheritance '${o.name}'");
}
// Class mixin is also available, and takes the form of
// class name extends SomeClass with AnotherClassName {}.
// It's necessary to extend some class to be able to mixin another one.
// The template class of mixin cannot at the moment have a constructor.
// Mixin is mostly used to share methods with distant classes, so the
// single inheritance doesn't get in the way of reusable code.
// Mixins follow the "with" statement during the class declaration.
/// Class mixin is also available, and takes the form of
/// class name extends SomeClass with AnotherClassName {}.
/// It's necessary to extend some class to be able to mixin another one.
/// The template class of mixin cannot at the moment have a constructor.
/// Mixin is mostly used to share methods with distant classes, so the
/// single inheritance doesn't get in the way of reusable code.
/// Mixins follow the "with" statement during the class declaration.
class Example23A {}
class Example23Utils {
addTwo(n1, n2) {
@ -351,10 +353,10 @@ example23() {
print("Example23 addTwo(1, 2) results in '${r2}'");
}
// The Class constructor method uses the same name of the class and
// takes the form of SomeClass() : super() {}, where the ": super()"
// part is optional and it's used to delegate constant parameters to the
// super-parent's constructor.
/// The Class constructor method uses the same name of the class and
/// takes the form of SomeClass() : super() {}, where the ": super()"
/// part is optional and it's used to delegate constant parameters to the
/// super-parent's constructor.
class Example24A {
var _value;
Example24A({value: "someValue"}) {
@ -372,9 +374,9 @@ example24() {
print("Example24 calling super during constructor '${o2.value}'");
}
// There's a shortcut to set constructor parameters in case of simpler classes.
// Just use the this.parameterName prefix and it will set the parameter on
// an instance variable of same name.
/// There's a shortcut to set constructor parameters in case of simpler classes.
/// Just use the this.parameterName prefix and it will set the parameter on
/// an instance variable of same name.
class Example25 {
var value, anotherValue;
Example25({this.value, this.anotherValue});
@ -385,9 +387,9 @@ example25() {
"'${o.anotherValue}'");
}
// Named parameters are available when declared between {}.
// Parameter order can be optional when declared between {}.
// Parameters can be made optional when declared between [].
/// Named parameters are available when declared between {}.
/// Parameter order can be optional when declared between {}.
/// Parameters can be made optional when declared between [].
example26() {
var _name, _surname, _email;
setConfig1({name, surname}) {
@ -407,13 +409,13 @@ example26() {
"email '${_email}'");
}
// Variables declared with final can only be set once.
// In case of classes, final instance variables can be set via constant
// constructor parameter.
/// Variables declared with final can only be set once.
/// In case of classes, final instance variables can be set via constant
/// constructor parameter.
class Example27 {
final color1, color2;
// A little flexibility to set final instance variables with syntax
// that follows the :
/// A little flexibility to set final instance variables with syntax
/// that follows the :
Example27({this.color1, color2}) : color2 = color2;
}
example27() {
@ -422,11 +424,11 @@ example27() {
print("Example27 color is '${o.color1}' and '${o.color2}'");
}
// To import a library, use import "libraryPath" or if it's a core library,
// import "dart:libraryName". There's also the "pub" package management with
// its own convention of import "package:packageName".
// See import "dart:collection"; at the top. Imports must come before
// other code declarations. IterableBase comes from dart:collection.
/// To import a library, use import "libraryPath" or if it's a core library,
/// import "dart:libraryName". There's also the "pub" package management with
/// its own convention of import "package:packageName".
/// See import "dart:collection"; at the top. Imports must come before
/// other code declarations. IterableBase comes from dart:collection.
class Example28 extends IterableBase {
var names;
Example28() {
@ -439,11 +441,11 @@ example28() {
o.forEach((name) => print("Example28 '${name}'"));
}
// For control flow we have:
// * standard switch with must break statements
// * if-else if-else and ternary ..?..:.. operator
// * closures and anonymous functions
// * break, continue and return statements
/// For control flow we have:
/// * standard switch with must break statements
/// * if-else if-else and ternary ..?..:.. operator
/// * closures and anonymous functions
/// * break, continue and return statements
example29() {
var v = true ? 30 : 60;
switch (v) {
@ -470,17 +472,17 @@ example29() {
} else {
continue;
}
// Never gets here.
/// Never gets here.
}
}
// Parse int, convert double to int, or just keep int when dividing numbers
// by using the ~/ operation. Let's play a guess game too.
/// Parse int, convert double to int, or just keep int when dividing numbers
/// by using the ~/ operation. Let's play a guess game too.
example30() {
var gn, tooHigh = false,
n, n2 = (2.0).toInt(), top = int.parse("123") ~/ n2, bottom = 0;
top = top ~/ 6;
gn = new DM.Random().nextInt(top + 1); // +1 because nextInt top is exclusive
gn = new DM.Random().nextInt(top + 1); /// +1 because nextInt top is exclusive
print("Example30 Guess a number between 0 and ${top}");
guessNumber(i) {
if (n == gn) {
@ -503,8 +505,8 @@ example30() {
}
}
// Optional Positional Parameter:
// parameter will be disclosed with square bracket [ ] & square bracketed parameter are optional.
/// Optional Positional Parameter:
/// parameter will be disclosed with square bracket [ ] & square bracketed parameter are optional.
example31() {
findVolume31(int length, int breath, [int height]) {
print('length = $length, breath = $breath, height = $height');
@ -514,12 +516,12 @@ example31() {
findVolume31(10,20); //also valid
}
// Optional Named Parameter:
// parameter will be disclosed with curly bracket { }
// curly bracketed parameter are optional.
// have to use parameter name to assign a value which separated with colan :
// in curly bracketed parameter order does not matter
// these type parameter help us to avoid confusion while passing value for a function which has many parameter.
/// Optional Named Parameter:
/// parameter will be disclosed with curly bracket { }
/// curly bracketed parameter are optional.
/// have to use parameter name to assign a value which separated with colan :
/// in curly bracketed parameter order does not matter
/// these type parameter help us to avoid confusion while passing value for a function which has many parameter.
example32() {
findVolume32(int length, int breath, {int height}) {
print('length = $length, breath = $breath, height = $height');
@ -529,9 +531,9 @@ example32() {
findVolume32(10,20);//also valid
}
// Optional Default Parameter:
// same like optional named parameter in addition we can assign default value for this parameter.
// which means no value is passed this default value will be taken.
/// Optional Default Parameter:
/// same like optional named parameter in addition we can assign default value for this parameter.
/// which means no value is passed this default value will be taken.
example33() {
findVolume33(int length, int breath, {int height=10}) {
print('length = $length, breath = $breath, height = $height');
@ -541,11 +543,11 @@ example33() {
findVolume33(10,20);//valid
}
// Programs have only one entry point in the main function.
// Nothing is expected to be executed on the outer scope before a program
// starts running with what's in its main function.
// This helps with faster loading and even lazily loading of just what
// the program needs to startup with.
/// Programs have only one entry point in the main function.
/// Nothing is expected to be executed on the outer scope before a program
/// starts running with what's in its main function.
/// This helps with faster loading and even lazily loading of just what
/// the program needs to startup with.
main() {
print("Learn Dart in 15 minutes!");
[example1, example2, example3, example4, example5, example6, example7,
@ -564,6 +566,3 @@ Dart has a comprehensive web-site. It covers API reference, tutorials, articles
useful Try Dart online.
[https://www.dartlang.org](https://www.dartlang.org)
[https://try.dartlang.org](https://try.dartlang.org)