pluckKey function
Plucks a single key's value from a Map (similar to getField but transform style).
Implementation
IValidator pluckKey(String key, IValidator child, {String? message}) {
return core.pivotValue(
(value) {
if (value is! Map || !value.containsKey(key)) return null;
return value[key];
},
child: child,
errorMessage: message ?? 'a Map containing key: $key',
);
}