Summary - Lists

Combine add, map and where to write a class list.

Summary - Lists

In this group you learned List creation, index access, add/remove, length/contains and the map/where methods. Now we will combine them to write a class-list application.

The app will append grades to a list with add and filter those 50 and above with where. This structure combines data entry and filtering; it is the core of a real grade-tracking app.

Plan

We will build the class-list app step by step: (1) declare an empty List<int>; (2) add a few grades with add; (3) filter those 50 and above with where; (4) convert the result to a List with .toList(); (5) print with print.

This structure is the skeleton of a real grade-tracking app too. Dropping low grades and listing the passing ones is common in schools and workplaces. Remember to convert the Iterable returned by where with .toList().

Exercise Class list app

Declare an empty int list with var grades = <int>[];. Add four grades with grades.add(40);, grades.add(55);, grades.add(70);, grades.add(30);. Declare a variable passing and assign the result of grades.where((g) => g >= 50).toList() to it. Print passing with print(passing);. The output on a single line must be [55, 70].

Show example solution

var grades = <int>[];
grades.add(40);
grades.add(55);
grades.add(70);
grades.add(30);
var passing = grades.where((g) => g >= 50).toList();
print(passing);

Test yourself

Write the add call

var grades = <int>[];
grades____;
grades.add(90);
print(grades);

Show answer

var grades = <int>[];
grades.add(85);
grades.add(90);
print(grades);

Which methods fit adding, filtering 50+ and transforming?
```
// class list
```
- add + where + map
- add + map + fold
- remove + length + contains
- add + sort + print
Show answer

add + where + map — add appends, where filters, map transforms.

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