I have a variable named number and a class which sets a variable to number in its constructor. I then change the value of number but the number in the class doesn't update. Here's my code:
void fn1() {
int number = 5;
SomeClass someClass = SomeClass(number);
// Do some other things which take a long time
number = 2;
someClass.printer(); // prints 5. expect 2
}
class SomeClass {
int nestedNum;
SomeClass(this.nestedNum) {
printer();
}
void printer() {
print(nestedNum);
}
}
How can I get nestedNum to update anytime number is changed?
So the hacky/easy solution would be anytime I change number in fn1, I need change nestedNum in someClass: like this: someClass.nestedNum = 2. The issue with that is if I have multiple classes I would have to go through each one to change the variable.
Another solution I thought of, was to never pass number into someClass, but instead pass this and access number using this. The issue with that is again, if I have multiple classes each needing to access a different variable from fn1.
The only way for nestedNum to change when number changes is to let nestedNum read from number. Dart does not allow references or pointers to variables to be passed around. What you can do is to pass a function to SomeClass which provides the value each time it's needed.
void fn1() {
int number = 5;
SomeClass someClass = SomeClass(() => number);
// Do some other things which take a long time
number = 2;
someClass.printer(); // prints 2!
}
class SomeClass {
final int Function() _nestedNum;
int get nestedNum => _nestedNum();
SomeClass(int Function() nestedNum) : _nestedNum = nestedNum {
printer();
}
void printer() {
print(nestedNum);
}
}
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