Null aware in dart


Come to this article to show that you must want to go a step further in DART’s Grammar (not surprisingly, you are learning flutter). This article will talk about the null aware operator in dart language!


DART’s null aware comes fromDart 1.12Official version:
Null aware in dart

You can also have a lookOfficial website version introduction


Since there is such a new operator, it shows that it is reasonable to some extentSaved our code, makeThe code is more concise.

Since it’s calledNull-aware, indicating that the operator is specializedFor processingnullvalueWill provide null pointer related operations

Null aware in dart

Create sample object

Let’s create onePersonObject, convenient for subsequent use:

class Person{
  String gender;
  //Change of gender to female
  void changeToFemale(){
    Gender = female;

Person person = Person();


When the current is null, the latter is returned

exp ?? anotherExp

Example: get user gender

When the gender attribute of a person object is null, ‘unknown’ is returned:

Method 1: basic if statement

We can use the most basic sentences to write:

String gender;
    gender = person.gender;
    Gender ='unknown ';

Method 2: three eye operation

The trinary operator is quite easy to use

String gender =  person.gender !=null ?  person.gender  : 'unknown';

It’s much better to do it in one line than if

Best solution:??operator

Use just learned??Operator handling:

String gender =  person.gender  ?? 'unknown';

It’s so simple


If obj is null, assign value to obj

obj ??= value

Example: default gender

If the gender property of the person object is null, it is assigned “male”

Let’s not use the stupid method here

person.gender  ?? = male;


When obj is not null, callmethodFunction:


Example: changing gender

When person is not null, change gender to female:


Call it a day!

If you follow the tutorial and everything goes well, Congratulations, you’ve learned a new way to save your life!


(ranking in any order)


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