Dart: converting _InternalLinkedHashMap<dynamic, dynamic> in constructor fails - json

Question

I am new to Dart and trying to deserialize some json, but I can't quite figure out the trick.
I am able to cast the Map in main as shown, but the commented code does not work and I can't figure out why. I feel like there must be an easier way to do this (outside of using a package for code generation), but I'm not sure what that is.
import 'dart:convert';
import 'dart:io';
class Book {
final String title;
final String path;
Book(this.title, this.path);
Book.fromJson(Map<String, dynamic> content)
: title = content['title'],
path = content['path'];
Map<String, dynamic> toJson() =>
{
'title': title,
'path': path,
};
String toString() {
return '{ title: $title, path: $path }';
}
}
class Books {
final Map<String, Book> bookList;
Books(this.bookList);
// Books.fromJson(Map<String, dynamic> content)
// : bookList = Map<String, Book>.from(jsonDecode(jsonDecode(content)['books']).map((k,v) => MapEntry(k as String, Book.fromJson(v))));
Map<String, dynamic> toJson() =>
{
'books': jsonEncode(bookList),
};
String toString() {
return bookList.toString();
}
}
void main() {
Map<String, Book> bookList = {
"foo": Book("Foo", "/foo"),
"bar": Book("Bar", "/bar"),
};
Books books = Books(bookList);
print(books);
String content = jsonEncode(books);
print(content);
// print(Books.fromJson(jsonDecode(content)));
Map<String, Book> m = Map<String, Book>.from(jsonDecode(jsonDecode(content)['books']).map((k,v) => MapEntry(k as String, Book.fromJson(v))));
print(m);
}

Answer 1

Oops, I needed to remove an invocation of jsonDecode from Books.fromJson...
Books.fromJson(Map<String, dynamic> content)
: bookList = Map<String, Book>.from(jsonDecode((content)['books']).map((k,v) => MapEntry(k as String, Book.fromJson(v))));