如何在ios中获取SSL证书的字符串形式的公钥

guard let certificatePath = Bundle.main.path(forResource: "certificate", ofType: "cer") else {
    // 证书文件路径错误
    return
}

guard let certificateData = NSData(contentsOfFile: certificatePath) else {
    // 证书文件加载失败
    return
}

guard let certificate = SecCertificateCreateWithData(nil, certificateData) else {
    // 证书创建失败
    return
}

guard let publicKey = SecCertificateCopyKey(certificate) else {
    // 公钥提取失败
    return
}

var error: Unmanaged<CFError>?
guard let publicKeyData = SecKeyCopyExternalRepresentation(publicKey, &error) as Data? else {
    // 公钥转换失败
    return
}

let publicKeyString = publicKeyData.base64EncodedString()