Question

假设：

sealed trait F
sealed trait K extends F
case object K1 extends K
sealed trait L extends F
case object L1 extends L

使用上面的层次结构，我如何定义一个函数，该函数在编译时具有类型A的列表，该列表全部为K或L ，即超类型必须是K或L，而不是F？

示例：

由于列表的超类型为f(List(K1, K1))

，

K会编译

但

f(List(K1, L1))不会，因为列表的超类型是F

Answer 1

你可以从Miles Sabin的答案开始Enforce type difference并改编：

 public void ConfigureAuth(IAppBuilder app)
    {

        // Configure the db context, user manager and signin manager to use a single instance per request
        app.CreatePerOwinContext(ApplicationDbContext.Create);
        app.CreatePerOwinContext<ApplicationUserManager>(ApplicationUserManager.Create);
        app.CreatePerOwinContext<ApplicationSignInManager>(ApplicationSignInManager.Create);

        // Enable the application to use a cookie to store information for the signed in user
        // and to use a cookie to temporarily store information about a user logging in with a third party login provider
        // Configure the sign in cookie
        app.UseCookieAuthentication(new CookieAuthenticationOptions
        {

            AuthenticationType = DefaultAuthenticationTypes.ApplicationCookie,
            LoginPath = new PathString("/Account/Login"),
            LogoutPath = new PathString("/Account/LogOff"),
            Provider = new CookieAuthenticationProvider
            {
                // Enables the application to validate the security stamp when the user logs in.
                // This is a security feature which is used when you change a password or add an external login to your account.  
                OnValidateIdentity = SecurityStampValidator.OnValidateIdentity<ApplicationUserManager, ApplicationUser>(
                    validateInterval: TimeSpan.FromMinutes(0),
                    regenerateIdentity: (manager, user) => user.GenerateUserIdentityAsync(manager))
            },
        });            
        //app.UseExternalSignInCookie(DefaultAuthenticationTypes.ExternalCookie);

        // these two lines of code are needed if you are using any of the external authentication middleware
        app.Properties["Microsoft.Owin.Security.Constants.DefaultSignInAsAuthenticationType"] = "ExternalCookie";
        app.UseCookieAuthentication(new CookieAuthenticationOptions
        {
            AuthenticationType = "ExternalCookie",
            AuthenticationMode = Microsoft.Owin.Security.AuthenticationMode.Passive,
        });

        // Enables the application to temporarily store user information when they are verifying the second factor in the two-factor authentication process.
        app.UseTwoFactorSignInCookie(DefaultAuthenticationTypes.TwoFactorCookie, TimeSpan.FromMinutes(5));

        // Enables the application to remember the second login verification factor such as phone or email.
        // Once you check this option, your second step of verification during the login process will be remembered on the device where you logged in from.
        // This is similar to the RememberMe option when you log in.
        app.UseTwoFactorRememberBrowserCookie(DefaultAuthenticationTypes.TwoFactorRememberBrowserCookie);
}

指定类型约束绑定

1 个答案: