LangageExt:用Bind()链接两个之一，但也不知道如何使用它们来创建另一个

Question

我使用LanguageExt在C#中具有函数式编程特性。我有一个方法，在这个方法中，我希望构建一个VaultSharp实例来访问我们的HashiCorp Vault服务。我的目标是通过两个参与者链创建一个VaultClientSettings实例(参见下面的方法)。最后，要么从链中的任意一个返回异常，要么从VaultClientSettings的实例返回异常。我认为我离得很近，但无法完成最后一步。我很感谢你的建议。

下面是指向C#的FP库和VaultSharp库的链接；

• https://github.com/louthy/language-ext/tree/main/LanguageExt.Core
• https://github.com/rajanadar/VaultSharp

下面的图片显示了我所看到的错误：

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            Either<Exception, Uri> GetVaultUri() =>
                EnvironmentVariable.GetEnvironmentVariable(KVaultAddressEnvironmentVariableName)
                    .Map(uri => new Uri(uri));

            Either<Exception, TokenAuthMethodInfo> GetAuthInfo() =>
                EnvironmentVariable.GetEnvironmentVariable(KVaultTokenEnvironmentVariableName)
                    .Map(token => new TokenAuthMethodInfo(token));

            Either<Exception, VaultClientSettings> GetVaultClientSettings(
                Either<Exception, Uri> vaultUri,
                Either<Exception, TokenAuthMethodInfo> authInfo
            )
            {
                /////////////////////////////////////////////////////////////////////////
                // I have access to the uri as u and the authmethod as a, but I cannot //
                // figure out how to create the instance of VaultClientSettings.       //
                Either<Exception, VaultClientSettings>  settings =
                    vaultUri.Bind<Uri>(u =>
                        authInfo.Bind<TokenAuthMethodInfo>(a =>
                        {
                            Either<Exception, VaultClientSettings> vaultClientSettings = 
                                              new VaultClientSettings(u.AbsoluteUri, a);

                            return vaultClientSettings;
                        }));
            }

Answer 1

没有使用这两个库，但是查看了Bind的签名

Either<L, B> Bind<B>(Func<R, Either<L, B>> f)

从签名判断，下列内容应有效：

Either<Exception, VaultClientSettings>  settings =
    vaultUri.Bind<VaultClientSettings>(u =>
        authInfo.Bind<VaultClientSettings>(a =>
        {
            Either<Exception, VaultClientSettings> vaultClientSettings = new VaultClientSettings(u.AbsoluteUri, a);

            return vaultClientSettings;
        }));

Answer 2

正如@hayden已经指出的:绑定类型参数是错误的(需要是“正确”的结果类型，无论哪种类型)。

对于LanguageExt:如果返回正确的类型，甚至可以省略类型参数：

Either<Exception, VaultClientSettings>  settings =
                    vaultUri.Bind(u =>
                        authInfo.Bind(a =>
                        {
                            Either<Exception, VaultClientSettings> vaultClientSettings = 
                                              new VaultClientSettings(u.AbsoluteUri, a);

                            return vaultClientSettings;
                        }));

此代码的另一种形式(LINQ)可能更易读：

var settings = from u in vaultUri
               from a in authInfo
               select new VaultClientSettings(u.AbsoluteUri, a);

本质上Bind是SelectMany (来自.)