service resolve

.swift

 func resolve(completion :@escaping (Blockchain) -> ())  {
        
        // get the nodes
        let nodes = self.blockchain.nodes
        
        for node in nodes {
            
            let url = URL(string :"http://\(node.address)/blockchain")!
            URLSession.shared.dataTask(with: url) { data, _, _ in
                
                if let data = data {
                  
                    let blockchain = try! JSONDecoder().decode(Blockchain.self, from: data)
                    
                    if self.blockchain.blocks.count > blockchain.blocks.count {
                        completion(self.blockchain)
                    } else {
                        self.blockchain.blocks = blockchain.blocks
                        completion(blockchain)
                    }
                    
                }
                
            }.resume()
            
        }
    }