Hola, I’m Hieu, a Software Engineer

Dependency injection has an intimidating name for an unremarkable idea: a class should be handed what it needs rather than constructing or locating it. That is the whole concept. Everything else — containers, locators, providers, generated code — is machinery for delivering it. The reason to care is testing. ApiClient() written inside a repository means every test of that repository makes real network calls. ApiClient passed in means every test can pass a fake. That is the entire payoff, and it is enough. Constructor injection, which needs no package final class UserRepository { const UserRepository ( this ._api, this ._cache); final ApiClient _api; final UserCache _cache; Future < User > fetch ( String id) async { final cached = _cache. get (id); if (cached != null ) return cached; final user = await _api. getUser (id); _cache. put (user); return user; } } Testing this requires no framework at all: test ( ...

Before records, returning two values from a function meant one of three unappealing options: a class you use once, a List<Object> you index into, or two out-parameters via a wrapper. Records make it one line. ({ int width, int height}) measure ( String text) { // ... return (width : 120 , height : 40 ); } final size = measure ( 'hello' ); print (size.width); That is the headline feature, and it is the smallest part of what records and patterns changed. Records: structural, not nominal A record’s type is its shape. (int, String) and (int, String) are the same type regardless of where they were created, which is what distinguishes a record from a class. // Positional ( String , int ) parseEntry ( String line) { final parts = line. split ( ':' ); return (parts[ 0 ], int . parse (parts[ 1 ])); } // Named — clearer at the call site ({ String name, int score}) parseNamed ( String line) { final parts = line. split ( ':...