Code snippet to explain a SSL pinning Alamofire and Server trust policy.

AlamofireAndServerTrustPolicies

// 1. Basic configuration for creating Alamofire manager
let configuration = URLSessionConfiguration.default
configuration.httpAdditionalHeaders = SessionManager.defaultHTTPHeaders
configuration.timeoutIntervalForRequest = 60

var serverTrustPolicies: [String: ServerTrustPolicy] = [:]

// 2. Pass your certificate filename, type and directory path to load the cefrtificate
guard let certificatePath = Bundle.main.path(forResource: "CertificateFileName", ofType: "der", inDirectory: "assets/certificate") else{
    print("OOPS! There is an error in certificate path")
}
let localCertificate: NSData = NSData(contentsOfFile: certificatePath)!

// 3. Set validateCertificateChain and validateHost to true for this certficate
let pinCertificate = ServerTrustPolicy.pinCertificates(
    certificates: [SecCertificateCreateWithData(nil, localCertificate)!],
    validateCertificateChain: true,
    validateHost: true
)

// 4. Set the loaded certificate for your dns.
// If the app is intended to connect with multiple backends, then set certificates for each backend system similarly.
serverTrustPolicies["www.example.com"] = pinCertificate

// 5. Create Alamofire session manager and set the server trust policies that we just created.
let manager = Alamofire.SessionManager(configuration: configuration, serverTrustPolicyManager: ServerTrustPolicyManager(policies: serverTrustPolicies))

// 6. Finally connect with the backend and trigger the rest service call
guard let url = URL(string: "https://www.example.com/restservice") else {
    print("Error in forming the URL")
}

// Desired parameters and headers
let parameters:Dictionary<String,String> = ["key1":"value1","key2":"value2"]
let headers =  ["Content-Type": "application/json", "Accept": "application/json"]

manager.request(url, method: .get, parameters: parameters, headers: headers)
    .validate()
    .responseJSON { response in
        guard response.result.isSuccess else {
            print("Error while fetching response \(response)")
            return
        }
        
        print("Success response received: \(response.result.value)")
        
}