Null safety in dart and flutter , the whole story!
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- Tony Hoare invented the null pointer in 1960 while developing the ALGOL programming language to handle errors when accessing array elements. - He later called the invention of the null reference his "billion dollar mistake" because it has led to many errors, vulnerabilities and system crashes over decades of use. - Dart's new null safety features make variables non-nullable by default and require handling null values explicitly to avoid errors. Migrating code to null safety involves adding question marks to variable types, handling null values, and using tools to help with the migration.
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Null safety in dart and flutter , the whole story!
- 1. Ahmed Abu Eldahab GDE Flutter & Dart @dahabdev Null Safety in Dart and Flutter , The whole Story!
- 2. Ahmed Abu Eldahab Google Developer Expert in Flutter & Dart Senior Technical Consultant Kortobaa LLC CTO /Dahabdev
- 4. 1960
- 5. Tony Hoare Sir Charles Antony Richard Hoare born 11 January 1934) - is a British computer scientist. He developed the sorting algorithm quicksort in 1959–1960.[5] He also developed Hoare logic for verifying program correctness. https://en.wikipedia.org/wiki/Tony_Hoare /DahabDev
- 6. - In 1960, Hoare left the Soviet Union and began working at Elliott Brothers. - After 9 months of programming he was asked to design a new programming language !! - Most software was still written in machine code. - In the library was a 23-page booklet entitled "Report on the international language ALGOL60" - He used it as a basis for the new language. - In order to implement error messages, an array had a check to verify whether its reference was in the bounds!. - Adding checks to arrays added space and time to the program !. - Then he went and invented the null pointer. Or he either have to check every reference. https://en.wikipedia.org/wiki/Tony_Hoare Tony Hoare in Moscow 1960 /DahabDev
- 7. Variables String name = ‘Ahmed’; Type Name Value /DahabDev
- 8. Memory Allocation String name = ‘Ahmed’; NameType Init val Address Value 0012CCGWH80 Ahmed Identifier Memory name /DahabDev
- 11. Null Pointer/Reference - A null pointer is a pointer that does not point to any memory location. - It represents an invalid memory location . - when a null value is assigned to a pointer then the pointer is considered as null pointer. /DahabDev
- 12. Null Pointer/Reference Exception (NPE) - Invoking a method from a null object. - Accessing or modifying a null object’s field. - Taking the length of null, as if it were an array. - Accessing or modifying the slots of null object, as if it were an array. /DahabDev
- 14. Something was called on null
- 15. Something was called on null /DahabDev
- 16. Null Pointer Exception (NPE) /DahabDev
- 17. Tony Hoare https://en.wikipedia.org/wiki/Tony_Hoare I call it my billion-dollar mistake. It was the invention of the null reference in 1965. ... This has led to innumerable errors, vulnerabilities, and system crashes, which have probably caused a billion dollars of pain and damage in the last forty years. 2009 /DahabDev
- 18. Tony Hoare https://en.wikipedia.org/wiki/Tony_Hoare - Null references have historically been a bad idea. - Programming language designers should be responsible for the errors in programs written in that language. - If the billion dollar mistake was the null pointer, the C gets() function is a multi-billion dollar mistake that created the opportunity for malware and viruses to thrive (Buffer overflow) /DahabDev
- 20. Important Expressions Dynamic Type system Static Type system Null Safety Unsound Null SafetySound Null Safety /DahabDev
- 22. Dart Null Safety Null safety is the largest change we’ve made to Dart since we replaced the original unsound optional type system with a sound static type system in Dart 2.0. /DahabDev
- 27. Dart Null Safety https://nullsafety.dartpad.dev /DahabDev
- 28. Dart Null safety principles /DahabDev Dart null safety support is based on the following three core design principles: ● Non-nullable by default. Unless you explicitly tell Dart that a variable can be null, it’s considered non-nullable. This default was chosen after research found that non-null was by far the most common choice in APIs. ● Incrementally adoptable. You choose what to migrate to null safety, and when. You can migrate incrementally, mixing null-safe and non-null-safe code in the same project. We provide tools to help you with the migration. ● Fully sound. Dart’s null safety is sound, which enables compiler optimizations. If the type system determines that something isn’t null, then that thing can never be null. Once you migrate your whole project and its dependencies to null safety, you reap the full benefits of soundness —- not only fewer bugs, but smaller binaries and faster execution https://dart.dev/null-safety
- 29. /DahabDev - All variables are non-nullable by default - If the variable can have the value null, add ? to its type declaration. String? name = null; - If you know that a non-nullable variable will be initialized to a non-null value before it’s used, but the Dart analyzer doesn’t agree, insert late before the variable’s type. late String name; Dart null safety roles https://dart.dev/null-safety
- 30. /DahabDev - When using a nullable variable or expression, be sure to handle null values. For example, you can use an if statement, the ?? operator, or the ?. operator to handle possible null values. String value = name ?? ''; // '' if it's null; otherwise, the String - If you’re sure that an expression with a nullable type isn’t null, you can add ! to make Dart treat it as non-nullable: String? name = 'Ahmed'; String value = name!; // `name!` is an String. // This throws if name is null. Dart null safety roles https://dart.dev/null-safety
- 31. Dart null safety roles /DahabDev - Once you opt into null safety, you can’t use the member access operator (.) if the operand might be null. Instead, you can use the null-aware version of that operator (?.): double? d; print(d?.floor()); // Uses `?.` instead of `.` to invoke `floor()`. - If you’re sure that an expression with a nullable type isn’t null, you can add ! to make Dart treat it as non-nullable: String? name = 'Ahmed'; String value = name!; // `name!` is an String. // This throws if name is null. https://dart.dev/null-safety
- 32. list, set, and map /DahabDev https://dart.dev/null-safety
- 33. list, set, and map /DahabDev https://dart.dev/null-safety
- 34. /DahabDev Migrating to null safety steps https://dart.dev/null-safety/migration-guide
- 35. /DahabDev Migrating to null safety steps https://dart.dev/null-safety/migration-guide
- 36. /DahabDev Migrating to null safety https://dart.dev/null-safety/migration-guide
- 37. /DahabDev Migrating to null safety https://dart.dev/null-safety/migration-guide
- 38. /DahabDev Migrating to null safety https://dart.dev/null-safety/migration-guide
- 39. /DahabDev Migrating to null safety https://dart.dev/null-safety/migration-guide
- 40. /DahabDev Migrating to null safety https://dart.dev/null-safety/migration-guide Everything is ok? HIT APPLY MIGRATION BUTTON !
- 41. /DahabDev Migrating to null safety https://dart.dev/null-safety/migration-guide
- 42. /DahabDev Migrating to null safety https://dart.dev/null-safety/migration-guide The analyzer can be wrong sometimes !
- 43. /DahabDev Migrating to null safety https://dart.dev/null-safety/migration-guide
- 44. /DahabDev How to practice Null safety? https://nullsafety.dartpad.dev
- 45. /DahabDev Migrating to null safety
- 46. Migrating to null safety /DahabDev 1. Wait for the packages that you depend on to migrate. 2. Migrate your package’s code, preferably using the interactive migration tool. 3. Statically analyze your package’s code. 4. Test to make sure your changes work. 5. If the package is already on pub.dev, publish the null-safe version as a prerelease version. https://dart.dev/null-safety
- 47. Thanks
- 50. Ahmed Abu Eldahab Google Developer Expert in Flutter & Dart Senior Technical Consultant Kortobaa LLC CTO /Dahabdev