String Interpolation Experiments

sql.swift

//
//  main.swift
//  StringLiterals
//
//  Created by Chris Eidhof on 21.02.19.
//  Copyright © 2019 objc.io. All rights reserved.
//

import Foundation

protocol SQLValue {}
extension Int: SQLValue {}
extension String: SQLValue {}

struct Query {
    var query: String
    var values: [SQLValue] = []
}

extension Query: ExpressibleByStringLiteral {
    init(stringLiteral value: String) {
        self.query = value
    }
}


extension Query: ExpressibleByStringInterpolation {
    struct StringInterpolation: StringInterpolationProtocol {
        var query: String
        var values: [SQLValue] = []

        init(literalCapacity: Int, interpolationCount: Int) {
        	print("\(literalCapacity) \(interpolationCount)")
            self.query = ""
            self.values = []
        }
        
        mutating func appendLiteral(_ literal: String) {
            query.append(literal)
        }
        
        mutating func appendInterpolation<V: SQLValue>(_ x: V) {
            query.append("$\(values.count)")
            values.append(x)
        }
    }
    
    init(stringInterpolation i: StringInterpolation) {
        self.query = i.query
        self.values = i.values
    }
}

let x: Query = "SELECT * from users where name == \("chris") AND age > \(20)"
print(x)