As the Container widget has a constraints instance variable 。 But the constructor will also has a constraints parameter.
And in the initializor list, We can see code like this:
constraints = (****） constraints;
So how do we know which constraints is reference to the instance variable , and which one is reference to the function parameter?
The name collision is not a problem in constructor initializer lists. The left-hand-side of each initialization may only be a member variable. From the Dart language specification:
Initializer Lists
An initializer list begins with a colon, and consists of a comma-separated list of individual initializers.
[...]
An initializer of the form v = e is equivalent to an initializer of the form this.v = e, both forms are called instance variable initializers.
Meanwhile, the expression on the right-hand-side cannot access this and therefore can never refer to a member variable. Therefore:
class Foo {
int x;
Foo(int x) : x = x;
}
has no ambiguity: the member variable x is initialized from the x parameter.
The name collision can be a problem in a constructor body, however:
class Foo {
int x;
Foo(int x) : x = x {
x *= 10; // This modifies the local `x` parameter.
}
}
In such cases, the constructor body must be careful to explicitly use this.x if it needs to use the member variable, not the parameter of the same name.
