Dart Optional NAMED Parameters in Functions. Dart Tutorial for Flutter #6.5

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Dart beginners guide. Dart has various Function Parameters such as Required Parameters, Optional Positional Parameters, Optional Named Parameters and Optional Default Parameters. In this video we will explore Optional Named Parameters.
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[@huzaifak_08]

Use the Keyword 'required int breath' in named parameter , who is facing issue in latest version of dart

[@MohammedAlmawali]

me

[@khoroshoigra8388]

I rushed my self to learn the flutter, for an exam about a job position in internal as mobile dev then luckily I found this great tutorial !!!!

[@sdmagic]

As in the previous video, Dart 3.0 changes the rules. It only allows null for parameters that are a nullable type. So, in the example given, you must provide a default value for the named parameters. Thus, the function becomes: void findVolume(int length, {int breadth = 10, int height = 30}) {... With that said, you can still reorder the parameters in the caller. So, for the function I gave here, you can still call it this way: findVolume(10, height: 20, breadth: 5); And finally, Dart 3.0 will not allow a function that's declared to return an integer to return a null. So, int findVolume() won't work. You must use: void findVolume().

[@nolssmit]

Updated (Dart 3) version: void main() { var result = getVolume(2, breadth: 3, height: 10); print("Volume is $result"); print(""); print("Circumference is ${getLength(2, height: 10, breadth: 3)}"); print(""); print("Circumference is ${getLength(2, breadth: 3)}"); } // Positional, (named and required parameters ... between curly brackets) int getVolume(int length, {required int breadth, required int height}) { print("height: $height breadth: $breadth length: $length"); return length * breadth * height; } // Positional, (named, required and optional parameters ... between curly brackets) int getLength(int length, {required int breadth, int height = 0}) { print("length: $length breadth: $breadth height: $height"); return length + breadth + height; }

[@Quvothe]

Thank you!

[@harrisoncorupe9178]

Really good info. Just needs to be updated to reflect dart having null safety.

[@saisasisai]

Nice 👌 Tutorial series ...!

[@achmadrf1243]

Hi, i've an issue that the syntax doesn't work when i don't use required keyword next to the parameter. How to solve it?

[@noob_gamer07]

if i make middle parameter as named parameter then it trouble shoot error

[@whitehawk4671]

Hey @Smartherd why my IDE is saying to add a required keyword while writing named parameter??

[@karthickrajalearn]

In 1m 28sec Thanks for Tip Named Parameter Purpose : Prevent Errors if function has large numbers of parameters Adavantage : Sequence does not a problem

[@hiteshgarg6303]

Please start flutter tutorial series also.

[@smartherd]

Soon after dart

[@flutterwithjt9345]

Hi @Smartherd. Can we use both positional and named parameters at the same time for the same parameter?

[@givenstudio6409]

yes you can

[@ranjeetbudhathoki1460]

why to use optional parameters?

[@NasGameOrg]

int function,,, says error.. void acceptable only

[@firasatali8395]

void main(){ findvolume(10, 20, 30); } int findvolume(int length, int breath, int height){ print("lenght is $length"); print("breath is $breath"); print("height is $height"); print("volume is ${length*breath*height}"); } I encountered an error : "The body might complete normally, causing 'null' to be returned, but the return type, 'int', is a potentially non-nullable type." so in beginning of the function had to remove "int". then it worked.

[@nikhiljohnjose6739]

Hi, I tried the Volume code but in the function definition it says "the parameter 'height' can't have a value of null because of it's type". That's one error.. when I removed the int from before the breadth and height, it didn't mark them as errors but in the function body breadth and height would be marked error ("A value of type num can't be assigned to variable of type int). Please help :) P.S: In the last video on positional parameters there was a similar error.. I had to remove String from inside the brackets e.g: [String name3] -> was an error [name3] -> got solved

[@TheChartwhisperers]

Add a required keyword e.g {required int height}

[@imranullah7722]

@@TheChartwhisperers but return type function is int also give error

[@imranullah7722]

watch this vedio you will b clear perfectly kzbin.info/www/bejne/bp-rqmmNp5eEn7c

[@sourabhsingh7491]

@@imranullah7722 use null null safety symbol after the datatype

[@rananomantariq4593]

hello hope your doing well can you pls tell us about function call backs in flutter or dart

[@rananomantariq4593]

or you can recomment a video pls hlp thank you

[@avi8034]

Since we have written ' int findVolume( ) ' , why we have not written a ' return length*breadth*height ' ? And my code was showing error when i printed it in the function itself then i printed it in main ( ) and it showed no error and got executed . Here is my code sir : void main ( ) { var result= findVolume(10, breadth:5, height:20); print("The Volume is $result"); } // Optional Named Parameters int findVolume(int length, {int breadth, int height} ) { return length*breadth*height; }

[@attimeequalszero6750]

What is the error message shown?

[@SeraphimTech_io]

Hi could you please start tutorial for python language? thx

[@smartherd]

Will ask Annie to make videos on python. It's in our queue

[@SeraphimTech_io]

thanks so much master

[@jashandeep5378]

I am running on visual studio

[@harshbarnwal1879]

from now in named parameters : is replaced by =

[@ithelightr3020]

Thanks Harsh

[@ithelightr3020]

But no thanks . It doesn't compile

[@TheChartwhisperers]

It’s been reverted back to :

[@tanaysingh9124]

why you didn't use return here?

[@attimeequalszero6750]

The function here is only printing the result and not returning any value back. The return type void would have been better in this example.

[@shafi.z7]

Instead of int use var

[@whatsaappstatus6452]

While using int in named parameters its showing error . Plz make it var and it will work 👍

[@kishansindhi6963]

Its due diff in versions. You can see the video was uploaded in 2018. There will be such kind of errors.

[@kishansindhi6963]

for more detail check this video kzbin.info/www/bejne/gaOcpJmflNV6apI

[@sifatcreator1175]

you don't show the default parameter

[@adeeba_rafi]

If found error write required before int here is the correct code void main() { findVolume(2, 3,height: 9); } void findVolume(int length, int breadth, {required int height }) { // In named Parameter Sequence doesnot matter print(height); print(breadth); print(height); print("${length * breadth *height}"); }

[@rockstreethomie]

named parameters not working

[@TheChartwhisperers]

Add required e.g {required int height}

[@delphinepauwels]

@@TheChartwhisperers but if I don't want a required parameter, but an optional one?

[@jashandeep5378]

void main() { Area1(10,2,height: 3); } void Area1(int lenth, int breath, {int height}){ int area=lenth*breath*height; print(area); } // Sir My Code is not working as this

[@benjaminmariga3938]

The error is occurring because you declared the height parameter as a non-nullable int type, but you're not providing a default value for it. To fix this issue, you have two options: A)you can provide a default value for the parameter example Area1(int lenth,int breadth,{int height=1})...... B)You make the parameter non-nullable Area1(int lenth,int breadth,{int? height}) //my code wasn't working and with these approaches it finally worked.Hope it helps

[@benjaminmariga3938]

void main() { int area = Area1(10, 2, height: 3); print(area); } int Area1(int lenth, int breath, {int? height}) { int area = lenth * breath * (height ??1); //I used the null-aware operator ?? to provide a default value of 1 when height is null return area;

[@firasatali8395]

void main(){ findvolume(10, breath:20, height:30); } findvolume(int length, {int breath, int height}){ print("lenght is $length"); print("breath is $breath"); print("height is $height"); print("volume is ${length*breath*height}"); } ENCOUNTERED AND ERROR IN ABOVE CODE: "The parameter 'breath' can't have a value of 'null' because of its type, but the implicit default value is 'null'. Try adding either an explicit non-'null' default value or the 'required' modifier. " "The parameter 'height' can't have a value of 'null' because of its type, but the implicit default value is 'null'. Try adding either an explicit non-'null' default value or the 'required' modifier." SOLUTION: remove "int" with-in the curly brackets before "breath" and "height" Ex:- findvolume(int length, { breath, height}){