Try To Avoid Weak-Strong Dance

WantToAvoidWeakStrongDance.swift

func weakToStrong<T: AnyObject>(on target: T, block: ((T) -> Void)?) -> Void {
    
    return { [weak target] in
        guard let target = target else {
            return
        }
        block?(target)
    }()
}

final class LoginViewModel {
    
    func login(loginId: String, password: String, completion: @escaping (Bool) -> Void) {
        
        // Want to avoid this weak-strong dance
        loginApiCall(loginId: loginId, password: password) { [weak self] token in
            
            guard let self = self,
                let token = token else {
                    completion(false)
                    return
            }
            
            // Something...
            
            completion(true)
        }
        
        
        // use weakToStrong
        loginApiCall(loginId: loginId, password: password) { token in
            
            weakToStrong(on: self) { (self) in
                guard let token = token else {
                    completion(false)
                    return
                }
                
                // Something...
                
                completion(true)
            }
        }
        
    }
    
    func loginApiCall(loginId: String, password: String,
                      completion: @escaping (String?) -> Void) {        
        completion("token")
    }
}