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| -rw-r--r-- | dart.html.markdown | 156 |
1 files changed, 136 insertions, 20 deletions
diff --git a/dart.html.markdown b/dart.html.markdown index f7c50b82..3e6ffe09 100644 --- a/dart.html.markdown +++ b/dart.html.markdown @@ -6,11 +6,12 @@ contributors: - ["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.~~ +**Dart** is a single threaded, general puprose programming languages. +It borrows a lot from other mainstream languages. +It supports Streams, Futures(known as Promises in JavaScript), Generics, First-class functions(closures) and static type checking. +Dart can run in any platform such as Web, CLI,Desktop, Mobile and IoT devices. -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's most controversial feature is its ~~Optional Typing~~ Static Type safety and [Sound Type checks](https://dart.dev/guides/language/sound-dart). ```dart import "dart:collection"; @@ -20,11 +21,53 @@ import "dart:math" as math; /// 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 + + +/// In Dart, Everything is an Object. +/// Every declaration of an object is an instance of Null and +/// Null is also an object. + + +/// 3 Types of comments in dart +// Single line comment +/** +* Multi-line comment +* Can comment more than 2 lines +*/ +/// Code doc comment +/// It uses markdown syntax to generate code docs when making an API. +/// Code doc comment is the recommended choice when documenting your APIs, classes and methods. + +/// 4 types of variable declaration. +/// Constants are variables that are immutable cannot be change or altered. +/// `const` in dart should practice SCREAMING_SNAKE_CASE name declaration. +const CONSTANT_VALUE = "I CANNOT CHANGE"; +CONSTANT_VALUE = "DID I?"; //Error +/// Final is another variable declaration that cannot be change once it has been instantiated. Commonly used in classes and functions +/// `final` can be declared in pascalCase. +final finalValue = "value cannot be change once instantiated"; +finalValue = "Seems not"; //Error + +/// `var` is another variable declaration that is mutable and can change its value. Dart will infer types and will not change its data type +var mutableValue = "Variable string"; +mutableValue = "this is valid"; +mutableValue = false; // Error. + +/// `dynamic` is another variable declaration in which the type is not evaluated by the dart static type checking. +/// It can change its value and data type. +/// Some dartisans uses dynamic cautiously as it cannot keep track of its data type. so use it at your own risk +dynamic dynamicValue = "I'm a string"; +dynamicValue = false; // false + + +/// Functions can be declared in a global space /// 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. +/// The fat arrow function declaration can be an implicit or +/// explicit return for the result of the expression. +/// Dart will execute a function called `main()` anywhere in the dart project. +/// example1() { nested1() { nested2() => print("Example1 nested 1 nested 2"); @@ -33,7 +76,7 @@ example1() { nested1(); } -/// Anonymous functions don't include a name. +/// Anonymous functions don't include a name but can take number of arguments example2() { //// Explicit return type. nested1(Function<void> fn) { @@ -43,10 +86,10 @@ example2() { } /// When a function parameter is declared, the declaration can include the -/// number of parameters the function takes by specifying the names of the +/// number of parameters the function takes by explicitly specifying the names of the /// parameters it takes. example3() { - planA(fn(informSomething)) { + planA(fn(String informSomething)) { fn("Example3 plan A"); } planB(fn) { /// Or don't declare number of parameters. @@ -57,6 +100,8 @@ example3() { } /// Functions have closure access to outer variables. +/// Dart will infer types when the variable has a value of something. +/// In this example dart knows that this variable is a String. var example4Something = "Example4 nested 1"; example4() { nested1(fn(informSomething)) { @@ -76,6 +121,7 @@ class Example5Class { example5() { /// Create an anonymous instance of the Example5Class and call the sayIt /// method on it. + /// the `new` keyword is optional in Dart. new Example5Class().sayIt(); } @@ -89,7 +135,7 @@ class Example6Class { } } example6() { - new Example6Class().sayIt(); + Example6Class().sayIt(); } /// Class methods and variables are declared with "static" terms. @@ -107,24 +153,68 @@ 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 +/// Dart supports Generics. +/// Generics refers to the technique of writing the code for a class +/// without specifying the data type(s) that the class works on. +/// Source: https://stackoverflow.com/questions/4560890/what-are-generics-in-c + +/// Type `T` refers to any type that has been instantiated +/// you can call whatever you want +/// Programmers uses the convention in the following +/// T - Type(used for class and primitype types) +/// E - Element(used for List, Set, or Iterable) +/// K,V - Key Value(used for Map) +class GenericExample<T>{ + void printType(){ + print("$T") + } + // methods can also have generics + genericMethod<M>(){ + print("class:$T, method: $M"); + } +} + + +/// List are similar to arrays but list is a child of Iterable<E> +/// Therefore Maps, List, LinkedList are all child of Iterable<E> to be able to loop using the keyword `for` +/// Important things to remember: +/// () - Iterable<E> +/// [] - List<E> +/// {} - Map<K,V> + + +/// List are great, but there's a restriction for what List can be +/// outside of function/method bodies. List 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"}; +/// declaring them "const". Kind of similar to Javascript's Object.freeze() +const example8List = ["Example8 const array"], +const example8Map = {"someKey": "Example8 const map"}; +/// Declare List or Maps as Objects. + List<String> explicitList = new List<String>(); + Map<String,dynamic> explicitMaps = new Map<String,dynamic>(); + + explicitList.add("SomeArray"); example8() { print(example8Array[0]); print(example8Map["someKey"]); + print(explicitList[0]); } +/// Assigning a list from one variable to another will not be the same result. +/// Because dart is pass-reference-by-value. +/// So when you assign an existing list to a new variable. +/// Instead of List, it becomes an Iterable +var iterableExplicitList = explicitList; +print(iterableExplicitList) // ("SomeArray"); "[]" becomes "()" +var newExplicitLists = explicitList.toList() // Converts Iterable<E> to List<E> + /// 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. +/// supported features, starting with forEach,map and where. var example9Array = const ["a", "b"]; example9() { - for (var i = 0; i < example9Array.length; i++) { + for (final i = 0; i < example9Array.length; i++) { print("Example9 for loop '${example9Array[i]}'"); } var i = 0; @@ -132,10 +222,12 @@ example9() { print("Example9 while loop '${example9Array[i]}'"); i++; } - for (var e in example9Array) { + for (final e in example9Array) { print("Example9 for-in loop '${e}'"); } + example9Array.forEach((e) => print("Example9 forEach loop '${e}'")); + } /// To loop over the characters of a string or to extract a substring. @@ -149,11 +241,34 @@ example10() { } } -/// Int and double are the two supported number formats. +/// `int`, `double` and `num` are the three supported number formats. +/// `num` can be either `int` or `double`. +/// `int` and `double` are children of type `num` example11() { var i = 1 + 320, d = 3.2 + 0.01; + num myNumDouble = 2.2; + num myNumInt = 2; + int myInt = 1; + double myDouble = 0; // Dart will add decimal prefix, becomes 0.0; + myNumDouble = myInt; // valid + myNumDouble = myDouble; //valid + myNumDouble = myNumInt; //valid + + myNumInt = myInt; // valid + myNumInt = myDouble; // valid + myNumInt = myNumDouble; // valid + + myInt = myNumDouble; //Error + myInt = myDouble; //Error + myInt = myNumInt; //valid + + myDouble = myInt; //error + myDouble = myNumInt; //valid + myDouble = myNumDouble; //valid + print("Example11 int ${i}"); print("Example11 double ${d}"); + } /// DateTime provides date/time arithmetic. @@ -248,8 +363,9 @@ example16() { print("Example16 join string array '${a.join()}'"); } -/// Strings can be concatenated by just having string literals next to +/// Strings can be concatenated by just having string List next to /// one another with no further operator needed. + example17() { print("Example17 " "concatenate " |