Ambiguous associated type error

help
1

Hi there, I have the following code

// Main struct for Solver
pub struct Solver<'a> {
    pub problem: &'a Problem,
    pub method: String
}

// Functions for Solver
impl Solver<'_> {
    pub fn run (&self) {
        // Print
        println!("Solving in Solver");

        let mut optimiser =  match self.method.as_str() {
            "GeneticAlgorithm" => GeneticAlgorithm::new {
                    problem: self.problem,     
        },
            _ => panic!()
        };
        optimiser.run();
    }
}

pub struct GeneticAlgorithm<'a> {
    pub problem: &'a Problem,
    initialization: Initialization,
    termination: Termination,
    is_initialized: bool

}


impl<'a> GeneticAlgorithm<'a> {
    fn new(problem: &'a Problem) -> Self {
        Self {
            problem: problem,
            initialization: Initialization {
                sampling: 3,
                repair: 3,
                eliminate_duplicates: 3
            },
            termination: Termination::new(),
            is_initialized: false

        }
    }
}

where I am trying to create a solver using struct. The solver requires parameters such as initialization and termination but I only want to pass the problem, and want the other parameters to take default values. The error i get is

error[E0223]: ambiguous associated type
  --> src/problem.rs:18:35
   |
18 |             "GeneticAlgorithm" => GeneticAlgorithm::new {
   |                                   ^^^^^^^^^^^^^^^^^^^^^ help: use fully-qualified syntax: `<GeneticAlgorithm<'_> as Trait>::new`

but I cannot seem to work out how to overcome my issue. Any help would be greatly appreciated!

2

You have mixed up struct literal syntax and function call syntax. This is valid syntax for a struct literal (though missing fields):

GeneticAlgorithm {
    problem: self.problem,     
}

and this is valid syntax for a function call to your GenericAlgorithm::new function, which looks like it'll do what you want:

GeneticAlgorithm::new(self.problem)

but GenericAlgorithm::new { would only be valid if new were a type of a struct (which is why the compiler mentioned 'associated type'), not a function.

(Rust has no “named arguments” for functions.)

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3

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