Posted on Apr 25, 2022

3 / 100DaysOfFlutter: Dart Sound Null Safety, Null Assign, Null Check, Everything null.

Learning null Safety in Dart:

understanding why we need null Safety; Null means nothing is there. so handle the programme at any point in time if there is a value which is null what should be performed?

Sound NullSafety:

By sound you might is understand that here you may know when the value will be null; so for that flow, we use SOUND Null Safety

 int i = 0; i= null; ❌ // here i is 0; but what if somepoint it becomes null; // then it will throw an error // so we need to add a check for null <!-- down arrow unicode --> int❓ j = 1; //^ this is a nullable variable; so in future it can be null; and wount' throw error.  // make any value nullable by adding ❓after the variable type.  j = null; ✅

List<String> names = ['Ram', 'Shyam', 'Hari']; names[0] = null; ❌ List<String?> names2 = ['Ram', 'Shyam', null]; names2[0] = null; ✅ List<String>? names3 = ['Ram', 'Shyam', 'Hari']; names3 = null ✅ // for making a list nullable we need to add ? after the list type here it is String. List<String?>? names4 = [null, null, "Ram"]; ✅ // Here List as well as list Type is also nullable.

Null Assign:

Null Assign means if the value is null Assign this value

int? age = 12; age = null; int RealAge = age ?? 18; // adding this ❓❓ after the variables (age) makes us sure that if any case the value of age is null the RealAge will be 18;

Null Check

Null check is a process of checking if the value is null or not, and perform tasks accordingly.

 List<String>? names5 = null; print(names5?.length); // it is shortcut for if(names5 != null) { print(names5.length); } else { print("null"); } print(Person?.skills?.length);✅ .❓.❓.❓ // it will only print the length of skills if the person is not null and if the skills are not null.