DAY 10
0
Mobile Development

04-Operators

playground9.dart

Code

``````void main() {
int num = 10 + 22;
num = num - 2;

print(num);

num = num % 5;
print(num);

// relational ==, !=, >=, <=
if (num == 0) {
print('Zero');
}

num = 100;
num *= 2; // num = num * 2
print(num);

// unary operator
++num;
num++;
num += 1;
num -= 1;
print(num);

// logical && and logical ||
if (num > 200 && num < 203) {
print('200 to 202');
}

// != Not Equal
if (num != 100) {
print('num is not equal to 100');
}
}
``````

Output

``````30
0
Zero
200
202
200 to 202
num is not equal to 100
``````

playground10.dart

• Null Aware Operator
• (?.), (??), (??=)

Code

``````class Num {
int num = 10;
}

main() {
var n = Num();
int number;

if (n != null) {
number = n.num;
}

print(number);

// part2 -- null error
// var n2;
// int number2;

// number = n2.num;

// print(number2);

// part3
var n3 = Num();
int number3;

number3 = n3?.num;

print(number3);

// part4
var n4;
int number4;

number4 = n4?.num ?? 0;

print(number4);

// part5
int number5;
print(number5 ??= 100);
print(number5);
}
``````

Output

``````10
10
0
100   /* ??= */
100
``````

playground11.dart

• Ternary operator

Code

``````void main() {
int x = 100;
var result = x % 2 == 0 ? 'Even' : 'Odd';
print(result);
}
``````

Output

``````Even
``````

playground12.dart

• Type test

Code

``````void main() {
int x = 100;

if (x is int) {
print('integer');
}
}
``````

Output

``````integer
``````

playground13.dart

• Conditional Statement

Code

``````void main() {
int number = 100;

if (number % 2 == 0) {
print('Even');
} else if (number % 3 == 0) {
print('Odd');
} else {
print('Confused');
}
}
``````

Output

``````Even
``````

playground14.dart

• Conditional Statement

Code

``````void main() {
int number = 20;
switch (number) {
case 0:
print('Even');
break;

case 1:
print('Odd');
break;

default:
print('Confused');
}
}
``````

Output

``````Confused
``````

05-Loop

playground15.dart

• Loop

Code

``````void main() {
// Standard for loop
for (var i = 1; i <= 10; ++i) {
print(i);
}
}
``````

Output

``````1
2
3
4
5
6
7
8
9
10
``````

playground16.dart

Code

``````void main() {
// for-in loop
var numbers = [1, 2, 3];

for (var n in numbers) {
print(n);
}

for (var i = 0; i < numbers.length; ++i) {
print(numbers[i]);
}
}
``````

Output

``````1
2
3
1
2
3
``````

playground17.dart

Code

``````void main() {
// forEach loop
var numbers = [1, 2, 3];

numbers.forEach((n) => print(num));
}
``````

Output

``````num
num
num
``````

playground18.dart

Code

``````void main() {
// forEach loop
var numbers = [1, 2, 3];

numbers.forEach((n) => print(n));
}
``````

Output

``````1
2
3
``````

playground19.dart

Code

``````void main() {
// forEach loop
var numbers = [1, 2, 3];

numbers.forEach(printNum);
}

void printNum(num) {
print(num);
}
``````

Output

``````1
2
3
``````

playground20.dart

Code

``````void main() {
// while loop
int num = 5;

while (num > 0) {
print(num);
num -= 1;
}
}
``````

Output

``````5
4
3
2
1
``````

playground21.dart

Code

``````void main() {
for (var i = 0; i < 10; ++i) {
if (i > 5) break;
print(i);
}
}
``````

Output

``````0
1
2
3
4
5
``````

playground22.dart

Code

``````void main() {
for (var i = 0; i < 10; ++i) {
if (i % 2 == 0) continue;
print('Odd: \$i');
}
}
``````

Output

``````Odd: 1
Odd: 3
Odd: 5
Odd: 7
Odd: 9
``````

06-Collection[List, Set, Map]

playground23.dart

Code

``````void main() {
// List
List names = ['Jack', 'Jill', 10, 100.1];

// Only Type: String
// List<String> names = ['Jack', 'Jill'];
print(names[0]);
print(names.length);

for (var n in names) {
print(n);
}

names[1] = 'Mark';

for (var n in names) {
print(n);
}

var names2 = [...names];
names[0] = 'Marry';

for (var n in names2) {
print(n);
}
}
``````

Output

``````Jack
4
Jack
Jill
10
100.1
Jack
Mark
10
100.1
Jack
Mark
10
100.1
``````

playground24.dart

Code

``````void main() {
// Set
var halogens = {'fluorine', 'chlorine'};

for (var x in halogens) {
print(x);
}
}
``````

Output

``````fluorine
chlorine
``````

playground25.dart

Code

``````void main() {
// Map
// Key:     Value
'first': 'partridge',
'secend': 'turtledoves',
'fifth': 'golden rings'
};
}
``````

Output

``````golden rings
``````

playground26.dart

Code

``````void main() {
// Map
// Key:     Value
2: 'partridge',
1: 'turtledoves',
3: 'golden rings'
};
}
``````

Output

``````turtledoves
``````

playground27.dart

Code

``````void main() {
// Map

}
``````

Output

``````Mongo
``````

playground28.dart

Code

``````void main() {
// Map
var gifts = {'first': 'Mongo', 'second': 'Jack Fruit'};

``````Jack Fruit