- Java Class
A class is a blueprint. It says what data an object holds and what it can do, and then you create objects from it. Every line of Java you have written so far lived inside one. Fields, constructor, methods Note that the class holds the data and the rules about that data together. The check in…
- React Native – Lists with FlatList
`ScrollView` renders every child immediately and holds them all in memory. `FlatList` virtualises — and on a phone that is the difference between a list that opens and one that hangs. `keyExtractor`, `renderItem`, header and empty components, multi-column grids, pull-to-refresh in two props, and why `numColumns` needs a `key` to change.
- Java Method
A method is a named block of code that takes inputs and optionally produces a result. Methods are how you stop repeating yourself and how you break a large problem into pieces small enough to understand one at a time. Anatomy public — who can call it. Packages covers the four options. int — the…
- React – Rendering Lists and Keys
Rendering an array with map, and the key prop React nags you about. What a key is actually for, why the array index is a bug waiting for the list to reorder, what to use when the items have no id, and why keys must be unique among siblings but not globally.
- Angular – Pipes
Formatting values in the template without cluttering the class. `DatePipe`, `CurrencyPipe`, `DecimalPipe` and `AsyncPipe`, chaining pipes and passing arguments, writing a custom pipe, and the pure-versus-impure distinction that decides whether your pipe runs once or on every change detection pass.