Dart Operators — Dart Programming — Part 4
Hello guys. So I’ve written 3 stories about dart basic. We’re going half way to learn basic about dart languages and i think it’ve enough preparation before you can take a step into Flutter World. So let me help you till the end. And, FlutterWithMe!
Today topic is about Operators. In dart we’ve many operators so i just take a quick look through there common.
There are math operator that help you calculate for number type in Dart.
int a = 8;
int b = 3;int sumAB() => a + b; // Result is 11
int subAB() => a - b; // Result is 5
int mulAB() => a * b; // Result is 24
double divAB() => a / b; // Result is 2.666
int divIntAB() => a ~/ b; // Result is 2
int modAB() => a % b; // Result is 2
And another operator is prefix and postfix increament and decreament operator.
int a;
int b;a = 0;
b = ++a; // Increment a before b gets its value.
assert(a == b); // 1 == 1
a = 0;
b = a++; // Increment a AFTER b gets its value.
assert(a != b); // 1 != 0
a = 0;
b = --a; // Decrement a before b gets its value.
assert(a == b); // -1 == -1
a = 0;
b = a--; // Decrement a AFTER b gets its value.
assert(a != b); // -1 != 0
Next one is Equality and relational operators
These operator can apply all for number but for string you only can use “== and !=” operator. If you want to compare two object, dart have function identical(). But with me, i prefer using Equatable for easier comparasion two object (which i’ll tell in another topic).
These operators are handly for checking types at runtime. “is and is!” return bool value for checking is correct type or not.
var name = "Hoang";bool checkIsString() => name is String; //result is true(name as int).toDouble(); //This'll cause error
But “as” is difference. It’ll force your variable to excatly type you want. And maybe cause error if it not this type. So be careful when using this one.
If you not sure about variable type, can check type like this.
var name = "Hoang";if (name is String) {
// Type check
name = 'Bob';
}
else if(name is int){
print("Not int type");
}
These operators help you combine many comparasion condition and priority which one want to pass first.
// This function need both isSupported == true and platform == "Android"if(isSupported && platform == "Android"){
print("Android platform supported");
}// This function need isSupported == true or platform == "Android"if(isSupported || platform == "Android"){
print("Supported or Android");
}// This function need both isSupported == true and platform == "Android" or "IOS"if(isSupported && ( platform == "Android" || platform == "IOS")){
print("Supported and android or ios platform");
}
Next one is what i favorites Conditional expressions. If you tired with write if else block, Dart have “? :” operator.
double paddingLeft = 0;if(Platform.isAndroid){
paddingLeft = 120;
}else {
paddingLeft = 60;
}// is similar with this one
paddingLeft = Platform.isAndroid ? 120 : 60;
Easy and perfect, you’re reduce code line to only one line. Other one is null-aware value.
String playerName(String? name){
if(name != null){
return name;
} else {
return "Guest";
}// is similar with this one
String playerName(String? name) => name ?? 'Guest';
Finally, let go to cascade operator and spread operator
I’ll take basic example about cascade operator and you’ll understand why i love it. It’s same line code but you’ll save effort when write this one, so try to use it into your code.
var address = getAddress();
address.setStreet(“Elm”, “13a”);
address.city = “Carthage”;
address.state = “Eurasia”
address.zip(66666, extended: 6666); // is similar with this one
getAddress()
..setStreet(“Elm”, “13a”)
..city = “Carthage”
..state = “Eurasia”
..zip(66666, extended: 6666);
Spread operator that help you insert another list into list. It’ll help you when code with Flutter in Row or Column (which i’ll talk in Flutter series).
/ main function startvoid main() {List list1 = ["Geeks","For","Geeks"];List list2=["Wow",...list1,"is","amazing"];print(list2);}
I think it’s long enough for Operators. Hope i help you have an overview about Dart enough. Thanks for reading!
