Easy Steps: Dart

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Dynamic variables and List

Number

int var_name;

double var_name;

why dclare type case language in dart

hold the data types dynamic and Static

Do (Rights) | Don't( Wrongs)

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int alpha99 | int 99alpha

int _name | int @name

int $name | int &name

| int #name

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var name =4;

print(name);

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var name =4;

name ='Johan'

print(name);

//Error: A value of type 'String' can't be assigned to a variable of type 'int'.

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When are you not sure with type of data is coming , So that cases declare as variable like that

var name;

name =44;

name ='Johan Doe';

print(name);

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Example: #1

dynamic firstName='Johan';

firstName=40;

print(firstName);

Example: #2 [dynamic]

List name=['Johan', 'Smith'];

print(name);

Example: #3

List job=[];

job.add('Software');

job.add(22);

print('$job');

Example: #4

List fruits=['Banana', 'Orange'];

fruits.add('KIWI');

fruits.add(22);

print(fruits);

print('$fruits');

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List<dynamic>name =['Johan', 'Smith', 33];

name.add(22);

print(name);

Example: #5 [ for loop ]

List<String> name=[];

for(int i=0;i<1; i++){

name.add('Hello World, ${i}');

print('$name');

print(name);

Example: #6[ add a different type ]

List <int> name=['Johan', 'Smith'];

print(name);

// Error: A value of type 'String' can't be assigned to a variable of type 'int'

Map [ dynamic ]

Example :#1

Map maps ={

"key": 'One Value',

2: 'Two Value'

};

print(maps);

Example :#2 [ Key, Value ]

Map<Key, value>

ie Key is key, 2,

Value is One Value, Two Value

Map <dynamic, String> maps ={

"key": 'One Value',

2: 'Two Value'

};

print(maps);

Example :#3 [ remove Duplicate, Values, Keys, toList, ]

Map <dynamic, String> maps ={

1:'Prince',

2:'Smith',

3: 'Johan'

};

print(maps.values);

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Map <dynamic, String> maps ={

1: 'Prince',

2: 'Smith',

3: 'Johan'

};

print(maps.keys);

Map <dynamic, String> maps ={

1:'Prince',

2:'Smith',

3: 'Johan'

};

print(maps.keys.toList()); //[1, 2, 3]

Expression or interpolate

Example :#1

String str1 = "hello";

String str2 = "world";

String res = str1+str2;

print("The concatenated string : ${res}");

Example :#2

String str1 = 'this is a single line string';

String str2 = "this is a single line string";

String str3 = '''this is a multiline line string''';

String str4 = """this is a multiline line string""";

print(str1);

print(str2);

print(str3);

print(str4);

Example :#3

print('${2+2}');

Example :#4

int n=1+1;

String str1 = "The sum of 1 and 1 is ${n}";

print(str1);

String str2 = "The sum of 2 and 2 is ${2+2}";

print(str2);

Example :#3 [final vs const ]

Dart throws an exception if an attempt is made to modify variables declared with the final or const keyword. The example given below illustrates the same -

Compile-time constants are constants whose values will be determined at compile time

if you never want to change a value then use fianl and const keywords

Difference between final and const ?

final variable can only be set once and it is initialized when accessed.

final name ="Peter" ;

final cityName ='Mumbai';

cityName ='Dubai';

//Error

const vriable is implicitly final but is a compile-time constants

> ie it is initialized during compilation

const pi =3.14

when you compile your program, in that sistutations pi will be initialized memory will be allocated.