Map
map分组
// String是key，可以是String或者int类型
//分组
Map<String, List<Brandinfos>> map = new Map.fromIterable(brandinfos,
key: (key) => key.firstLetter,
value: (value) {
return brandinfos.where((item) => item.firstLetter == value.firstLetter).toList();
});
//或
Map<String, List<Brandinfos>> mapBrandinfos = groupBy(brandinfos, (Brandinfos.firstLetter) => brandinfo.firstLetter);
map 排序
final Map<String, List<Brandinfos>> mapBrand = SplayTreeMap.from(map, (a, b) => a.compareTo(b));
map便利
mapBrand.forEach((k,v) {
print('$k --- ${v.map((value) => value.name).join(",")}');
});
