This Guide is for those, who were/are already familiar to programming and have desire to learn dart also for various purposes.
Links :
Note : This guide not gonna brush over the simple programming facts like
- what is loop ?
- what is datatype ?
- what is condition statement ?
- what is variable ? and so on.
If you are unfamiliar with any of above terms take a slight look on this terms before starting.
First of all we gonna cover basic syntax and topics on of dart language like :
- Data Types
- How to Define A Variable
- Print Statement in Dart
- Different operators in Dart
- Loops in Dart
- If Else Statement in Dart
- Function in Dart
Before We go onto basics, let us see an hello world program in dart language
main(){
print("Hello World");
}Before Starting : All datatypes in dart are at base is just an object. Value of each variable declared using these datatype is null by default.
More Remarks :
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Dart is statically typed language means you have to explicitly declare variable's datatype and it cannot be changed at runtime.
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var keyword is used to auto declare the datatype of variable but dissimilar of var in js once variable datatype set using var keyword it can't be changed.
Note : by default var assign the dynamic datatype to variable but it can be differ if you initialize the variable during declaration.
var var1 ;//dynamic var1 = 'a'; var1 = 2;//No Errors var var2 = 123;//int var2 = "fire";//Error: A value of type 'String' can't be assigned to a variable of type 'int'.
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dynamic keyword which is dart object under the hood is used to dynamically assign datatype to variable it associated with.
dynamic a = 40; a ='a'; //works a = true; a = ['a','b',2,true];
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holds the numeric value. The num type is an inherited data type of the int and double types.
| Keyword - num |
Number in dart can further classified as: int used to represent integers double used to represent floating point values
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is used to represent whole numbers values.
| Keyword - int |
int mynum = 4; int mynum2 = 9999; int mynum3 = -232; //below code will give an error int mynum4 = 33.34;//Error: A value of type 'double' can't be assigned to a variable of type 'int'. //Note : Sometime you may need to convert int to string datatype at this you may use toString method in-built to num object. print("1 "+ mynum.toString()); print("2 "+ mynum2.toString()); print("3 "+ mynum3.toString()); /*Output : 1 4 2 9999 3 -232 */
is used to represent 64-bit floating-point numbers.
| **Keyword** - double | ```dart double mynum = 434.22; double mynum1 = -4331.233; double mynum2 = 32; //Note : Sometime you may need to convert double to string datatype at this you may use toString method in-built to num object. print("1 "+ mynum.toString()); print("2 "+ mynum1.toString()); print("3 "+ mynum2.toString()); /*Output: 1 434.22 2 -4331.233 3 32 */ ```For more detail on Number, Int, Double class and their property
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is used to represent a sequence of characters. It is a sequence of UTF-16 code units. The keyword string is used to represent string literals.
| Keyword - String |
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In dart string is represent as text between ""(double quotes) or ''(single quotes ) also known as String Literals.
String mystr = "hello"; String mystr2 = "dart"; String mystr3 = "652"; String mystr4 = 54; //Error: A value of type 'int' can't be assigned to a variable of type 'String' //String mystr4 = 54; print("1 "+mystr); print("2 "+mystr2); print("3 "+mystr3); /*Output 1 hello 2 dart 3 652 */
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represents Boolean values true and false.
The keyword bool is used to represent a Boolean literal in DART.
| Keyword - bool |
bool mybool = false; bool mybool1 = true; bool mybool2 = 1;//Error: A value of type 'int' can't be assigned to a variable of type 'bool'. bool mybool3 = 0;//Error: A value of type 'int' can't be assigned to a variable of type 'bool'. bool mybool4; bool mybool5 ="true";//Error: A value of type 'String' can't be assigned to a variable of type 'bool'. bool mybool6 ="false";//Error: A value of type 'String' can't be assigned to a variable of type 'bool'. print("1 "+mybool.toString()); print("2 "+mybool1.toString()); print("3 "+mybool4.toString());//null is no value is given
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is similar to arrays in other programming languages. A list is used to represent a collection of objects. It is an ordered group of objects.
| Keyword - List |
Remarks : . The dart:core library provides the List class that enables creation and manipulation of lists.
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In this type of list, length can't change at runtime.
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Declaration Syntax :
List Declare using this syntax will be fixed size list.
List list-name = new List(initialization_size);
Intializing list element after declaration
List myList = new List(n); myList[index] = val;//index can be any value between 0 to n-1
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Example of Nested Lists :-
List myList = new List(6); for(int i=0;i<6;i++){ myList[i]= "hello "+i.toString(); } List myList2 = ["one",2,"three"]; List myList3 =[myList,myList2]; print(myList); print(myList2); print(myList3); /* Output : [hello 0, hello 1, hello 2, hello 3, hello 4, hello 5] [one, 2, three] [[hello 0, hello 1, hello 2, hello 3, hello 4, hello 5], [one, 2, three]] */
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->Syntax is same as of Fixed List but you can add more element, change the length of current List object via add() method. Note : A list is resizable only if initialized using following syntax;
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Syntax1 :
List l = new List();//empty initialization of list using constructor with no para //l is a variable-name
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Syntax2 :
List l = []; //Using List literal or List l = [val1,val2,...val_n]; //l is a variable-name
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First method:
List myList = new List(); myList.add(1); myList.add(2); myList.add(3); myList.add("hy"); myList.add("true"); myList.add(true); //i won't recommend this if input value need to be changed after initialization.
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Second method:
List myList2 = ['a','b','c'];//resize the existing list myList2.add(4); print(myList); print(myList2); /*Output [1, 2, 3, hy, true, true] [a, b, c, 4] */ myList2[4] ="five";//This generate out of index error.
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More Examples :
List myList = new List(6); for(int i=0;i<6;i++){ myList[i]= "hello "+i.toString(); } List myList2 = ["one",2,"three"]; myList2.add(3); List myList3 =[myList,myList2]; var myList4 = new List(); myList4.add(5); // myList3[2]=5; print(myList); print(myList2); print(myList3); print(myList4); /*Output [hello 0, hello 1, hello 2, hello 3, hello 4, hello 5] [one, 2, three, 3] [[hello 0, hello 1, hello 2, hello 3, hello 4, hello 5], [one, 2, three, 3]] [5] */
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List l = new List(2);//Fixed Size List l[0]=2; l.add(1);//It will Throw //Unsupported operation: addError: Unsupported operation: add print(l); List p = new List(); p.add(2);//No problem
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object is a key and value pair. Keys and values on a map may be of any type. It is a dynamic collection.
| Keyword - Map |
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Syntax :
Map myMap = new Map(); myMap[key1] =val1; myMap[key2] =val2; myMap[key3] =val3; .... myMap[key_n] =val_n; //val1,val2,val3...val_n can be of any datatypes, objects etc. //key1,key2,key3...key_n can be of any datatypes,objects etc.
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Example :
Map obj = new Map(); obj["mykey"] ="myVal";//String as key List l = [1,2,3];//list obj[l] ="list as key";//list as key obj[true] =false;//boolean value as key obj[23] =43;//integer value as key print(obj["mykey"]); print(obj[l]); print(obj[true]); print(obj[23]); /*Output : myVal list as key */
Note while using list or any other object as key that it will take the reference of obj as key not the value of object itself.
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Example :
Map myMap = new Map(); List l = [1,2,3];//list obj[l] ="List as key"; print("Before : "+ obj[l]); l[1] = 4;//changes print("After : "+obj[l]);//same result /*Output Before : List as key After : List as key */ //More obj[[5,6,7]]= "Another One"; print(obj[[5,6,7]]); //and also print(obj[[1,2,3]]); //since l is reference to object of List which is new for each list print([1,2,3]==l);//Example
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Actually, it can be both interpreted and compiled. Yes, it provides functionality for ahead of time (AOT) compilation used primarily in production code and also for just in time compilation which is beneficial while developing code.
Commands for compiling different dart executables :
dart compile <sub-command> <dart-file>
sub-commands overview aot-snapshot Compile Dart to an AOT snapshot. exe Compile Dart to a self-contained executable. jit-snapshot Compile Dart to a JIT snapshot. js Compile Dart to JavaScript. kernel Compile Dart to a kernel snapshot Example (for binary system executable) :
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Creating
dart compile exe main.dart
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Running (in linux env)
./main.exe
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