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Questions tagged [null-safety]

96 questions
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How to take integer input from user in dart

i am new in dart and just want to know how to take integer input from user in dart with null safety. i found out a way to take number input from dart which is: String? chossenNumber = stdin. readLineSync(); if(chossenNumber !=null) { int…
Saad Ebad
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Is there a way in PHP to use null coalesing/nullsafe operators to default to not set any value?

I only see use cases were null coalesing can be used to chain values, but not to omit any value. Am I missing something essential or is there really no shorthand way to write this: $model->name = "Example"; if(isset($input->name)) { $validName…
Alex
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The argument type 'List?' can't be assigned to the parameter type 'List?'

i have recently migrated my code to null safety. got the below error in dart migrate command. The argument type 'List?' can't be assigned to the parameter type 'List?' at…
Venki
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1 answer

Null aware assignment of map entry

Is there an elegant way to write the following statement for a map? String? img = json['image']; if (img != null) { json['image'] = 'https://example.com/ingredients_100x100/' + img; } Basically I want to append the image IFF it exists and…
lhengl
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Stateful Classes Flutter project

I'm trying to generate a Flutter app, to create a stateful text field that I can call from other class (passing a name of the field and a limit for the field)., but I don't know how to do that, Basically, I'm trying to be concise and reduce the…
MoStafa SelieM
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3 answers

Why im getting this error Warning: Operand of null-aware operation '??' has type 'String' which excludes null. Dart Language

so i was learning about SWITCH and CASE Statements in dart language, in the course he explains the code but he don't get an error while i get one. the error i get : Warning: Operand of null-aware operation '??' has type 'String' which excludes…
Yamix.co
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Firebase doesn't work cause of null-safety (DART/FLUTTER)

I'm using/learning Firebase for my database works. My snapshot's coming like _jsonQuerySnapshot or _jsonDocumentSnapshot. But it had to be QuerySnapshot or DocumentSnapshot. Because of this I have to encode and decode my snapshot for use my…
demonjoseph
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How can I solve this Flutter GraphQL null safety error?

I'm trying to use graphql_flutter's Subscription widget but my app fails to compile. I keep getting a null safety error: Error: The argument type 'Widget Function({dynamic error, bool loading, dynamic payload})' can't be assigned to the parameter…
Omojola Samson
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Unhandled Exception: Looking up a deactivated widget's ancestor is unsafe Navigator.push after migration to null safety

I have migrated all my packages of the project to null safety. Due to some thinks that I have to handle on the Android (Kotlin), extending a third party library. After doing that now I receive the following error: E/flutter (14210):…
el.severo
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Method 'showBottomSheet' cannot be called on 'ScaffoldState?' because it is potentially null

Hello I'm getting this error when I tried to run the code lib/layout/home_layout.dart:54:36: Error: Method 'showBottomSheet' cannot be called on 'ScaffoldState?' because it is potentially null. - 'ScaffoldState' is from…
Diaa Nassar
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indicates versions without null safety support

I'm tryna enabled null-safe property. that's why I wrote "dart pub outdated --mode=null-safety" but I got error below: indicates versions without null safety support
zey.s
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The property 'xyz' can't be unconditionally accessed because the receiver can be 'null'

I was upgraded my flutter project version to the latest (2.5.3). then occurred some errors due to unsupported null-safety. I had fixed many but still, haven't any idea to fix following null-safety to error, Code itemBuilder: (context, suggestion) { …
Tharindu Lakshan
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