How to dynamically instantiate a class (Function.apply for class)? - dart

Question

In Dart, I can dynamically call a function using Function.apply:
Function.apply(foo, [1,2,3], {#f: 4, #g: 5});
gives exactly the same result as
foo(1, 2, 3, f: 4, g: 5).
Question: Does a similar thing exist for instantiating classes?
Expected result would look something like:
class foo {
final String boo;
int? moo;
foo({required this.boo, this.moo})
}
...
var params = {boo: 'A string value', moo: 121};
Class.apply(foo, params);
// Gives the result:
foo(boo: 'A string value', moo: 121);

Answer 1

Function.apply isn't type-safe, so you should avoid using it if you can.
If you really want to use it with a constructor, you can use it with constructor tear-offs (added in Dart 2.15), which are just Functions:
class Foo {
final String boo;
int? moo;
Foo({required this.boo, this.moo});
#override
String toString() => 'Foo(boo: "$boo", moo: $moo)';
}
void main() {
var params = {#boo: 'A string value', #moo: 121};
var result = Function.apply(Foo.new, [], params);
print(result); // Prints: Foo(boo: "A string value", moo: 121)
}

Answer 2

As far as I know, you can make use of static methods if you want to create an instance without using another instance. Here is a sample:
class Foo {
final String boo;
final int moo;
Foo({this.boo, this.moo});
static fromValues({String boo, int moo}) {
return Foo(boo: boo, moo: moo);
}
}
void main() {
var params = {#boo: 'A string value', #moo: 121};
var fooObject = Function.apply(Foo.fromValues, [], params);
print(fooObject);
print(fooObject.boo);
print(fooObject.moo);
}
Another way is to add 'call' function to class to make it's objects callable and use an object of the class to create new objects. Here is a sample:
class Foo {
final String boo;
final int moo;
Foo({this.boo, this.moo});
call({String boo, int moo}) {
return Foo(boo: boo, moo: moo);
}
}
void main() {
Foo aFoo = Foo(boo: 'nothing', moo: 0);
var params = {#boo: 'A string value', #moo: 121};
var fooObject = Function.apply(aFoo, [], params);
print(fooObject);
print(fooObject.boo);
print(fooObject.moo);
}