addFilter method
Add a filter.
socials.addFilter(
<String>['upper', 'uppercase', 'touppercase'], (String value) =>
value.toUpperCase());
Implementation
void addFilter(List<String> names, String Function(String) func) {
for (final String name in names) {
if (filters.containsKey(name)) {
throw DuplicateNameError(name);
}
filters[name] = func;
}
}