Dart Programming

Dart Nulls

“A value in a database is zero. The value null denotes the absence of a value. Null is not a memory location when it is used as a value. Only pointers store memory locations. A string would not terminate correctly if it lacked a null character, causing problems. In the Dart programming language, null is symbolized by the keyword null. In Dart also, Null refers to a variable that has never had any values assigned to it and was created with nothing. This article will cover how to handle Null type in Dart programming language.”

What is the Null-Aware Operator in a Dart in Ubuntu 20.04?

Dart’s null-aware operators let you compute according to a value is null or not. It’s a shorter version of a longer statement. Instead of issuing an error, a null-aware operator makes nullable types accessible in Dart. These operators are coupled in this order so that you end up with a value instead of a null. To identify whether such a variable’s value is null, null-aware operators are almost universally employed in programming languages. The Null aware operator is most widely used when a developer wishes to extract JSON data from a server and then use the IF-Else condition to verify whether JSON is empty or not.

How to Use the Null-Aware Operator in the Dart in Ubuntu 20.04?

Dart offers several null-aware operators that we may use to ensure that we don’t access null values and to handle them subtly. We have some basic null-aware operators below, which are used in the dart scripts.

Example # 1: Using the Null Object in a Dart in Ubuntu 20.04

Here, we have a representation of a null object that shows how the dart compiler throws an error when encountered with the null object.

We built a Person, and within the class, we have a variable named “person_name” in the above dart code. We defined a variable type string and initialized it with the string of words. The class object is created inside the main() method as persons by calling the class named “Person.” Here, we have tried calling the object with the null declaration. However, we receive an error whenever we execute the program above.

Thus, you can see the “NoSuchMethodError” exception is thrown by the dart compiler. This means that we cannot utilize non-nullable objects before it is assigned.

Example # 2: Using the Safe Navigation Operator “?.” in a Dart in Ubuntu 20.04

When we don’t want to call a function with a null value, we utilize the? Operator. If the value is not null, it will invoke a function.

We have constructed the dart main method, and inside it, we have generated a variable “myVal.” We haven’t set the variable “myVal” as you can see.” So it contains a null as its value in the code. Then, we have invoked a length function on the variable “myVal” with the safe navigation operator “?” in the variable “length.” This will change nothing as the variable “length” is also a null value.

The null is printed on the screen from the above dart code as null is itself a value.

Example # 3: Using the Default Operator “??” in a Dart in Ubuntu 20.04

When evaluating and returning a statement, if the other expression evaluates to null, we use the default operator “??”. It’s also known as the if-null and coalescing operators. The default operator “??” is a null-aware operator that returns the expression to its left unless its value is null. If it’s null, the expression is returned in its original position.

Above, we have a string that we have assigned to the variable “str1”. Then, using a default operator, we generated another string variable “??” over a string “str1”. This operator will return the string value as the variable is not null. On the other side, we’ve defined a variable called “str3” that is currently null. So we have built another variable, “str4”, which utilizes the default operator “??” on a variable “str3” and will return a value “sweet” written after the default operator inside the variable “str4”.

The results of the default operator from the above dart code are as follows.

Example # 4: Using a Default Assignment Operator in a Dart in Ubuntu 20.04

When we prefer to assign a value only if it is not null, we utilize the??= operator in Dart.

Within the dart main method, we have a variable “color,” which is null. The other variable, “mycolor,” is defined with the string value. When we tried to allocate the value of the “color” variable to the “mycolor” variable, nothing happened because “color” is null, and so the operator “??=” doesn’t affect the original value of the “mycolor” variable.

The value “Blue” is printed by the dart compiler as follows:

Example # 5: Assigning Non-Nullable Variable in a Dart in Ubuntu 20.04

The analyzer in Dart can tell you if a nullable property is assured to contain non-null data by notifying you what compile-time errors and warnings you have. Dart employs Flow Analysis to promote types at runtime (data flow of a program is determined via flow analysis.)

We have created an int function “checkNull” and passed an object “myvalue” with the safe navigation operator “?” which tells us that the object is null. Then, we have an if statement inside our function. In the above-mentioned code, the if statement determines whether or not the object is null. After the if statement, the data cannot be null and is treated as a non-nullable object (promoted). This enables us to make use of myvalue. abs() rather than myvalue? abs() with optimism while using the null-aware operator. In this example, the abs() method returns an absolute number. After that, we have printed the values, which are passed to the function “checkNull” inside the dart main method.

The results of the above dart program are as shown:


Ended up here, we have explored the null-aware operator examples in the dart code. Now, we all know how to use and where to use the various null operators in the dart programming language. The null-aware operators allow for more productive application development with fewer runtime problems. Our code will be optimized by Dart Compiler.

About the author

Saeed Raza

Hello geeks! I am here to guide you about your tech-related issues. My expertise revolves around Linux, Databases & Programming. Additionally, I am practicing law in Pakistan. Cheers to all of you.