Merge branch 'master' of https://github.com/altmann/FluentResults

Author: altmann

README.md

@@ -327,7 +327,7 @@ Result.Ok<int>(5).ToResult<float>(v => v);
 Result.Fail<int>("Failed").ToResult<float>();
 
 // converting a result to a result from type Result
-Result.Ok<int>().ToResult(); 
+Result.Ok<int>().ToResult();
 ```
 
 ### Implicit conversion from T to success result ```Result<T>```
@@ -337,6 +337,41 @@ string myString = "hello world";
 Result<T> result = myString;
 ```
 
+### Bind the result to another result
+
+Binding is a transformation that returns a `Result` | `Result<T>`.
+It only evaluates the transformation if the original result is successful.
+The reasons of both `Result` will be merged into a new flattened `Result`.
+
+```csharp
+// converting a result to a result which may fail
+Result<string> r = Result.Ok(8)
+    .Bind(v => v == 5 ? "five" : Result.Fail<string>("It is not five"));
+
+// converting a failed result to a result, which can also fail, 
+// returns a result with the errors of the first result only,
+// the transformation is not evaluated because the value of the first result is not available
+Result<string> r = Result.Fail<int>("Not available")
+    .Bind(v => v == 5 ? "five" : Result.Fail<string>("It is not five"));
+
+// converting a result with value to a Result via a transformation which may fail
+Result.Ok(5).Bind(x => Result.OkIf(x == 6, "Number is not 6"));
+
+// converting a result without value into a Result 
+Result.Ok().Bind(() => Result.Ok(5));
+
+// just running an action if the original result is sucessful. 
+Result r = Result.Ok().Bind(() => Result.Ok());
+```
+
+The `Bind` has asynchronous overloads.
+
+```csharp
+var result = await Result.Ok(5)
+    .Bind(int n => Task.FromResult(Result.Ok(n + 1).WithSuccess("Added one")))
+    .Bind(int n => /* next continuation */);
+```
+
 ### Set global factories for ISuccess/IError/IExceptionalError
 
 Within the FluentResults library in some scenarios an ISuccess, IError or IExceptionalError object is created. For example if the method ```Result.Fail("My Error")``` is called then internally an IError object is created. If you need to overwrite this behavior and create in this scenario a custom error class then you can set the error factory via the settings. The same extension points are also available for ISuccess and IExceptionalError. 

src/FluentResults.Test/Playground.cs

@@ -1,5 +1,7 @@
 using System;
 using System.Collections.Generic;
+using System.Threading.Tasks;
+using FluentResults.Extensions;
 
 namespace FluentResults.Test
 {
@@ -21,31 +23,30 @@ public void Simple()
             var voidResult = Result.Ok();
 
             voidResult = Result.Ok()
-                .WithSuccess("This is a success")
-                .WithSuccess("This is a second success");
+                               .WithSuccess("This is a success")
+                               .WithSuccess("This is a second success");
 
             voidResult = Result.Fail("First error");
 
             voidResult = Result.Fail(new Error("First error"));
 
             voidResult = Result.Fail("First error")
-                .WithError("second error")
-                .WithError(new CustomError().CausedBy(new InvalidCastException()));
-
+                               .WithError("second error")
+                               .WithError(new CustomError().CausedBy(new InvalidCastException()));
 
             var valueResult = Result.Ok<int>(default)
-                .WithSuccess("first success")
-                .WithValue(3);
+                                    .WithSuccess("first success")
+                                    .WithValue(3);
 
             valueResult = Result.Ok(3);
 
             valueResult = Result.Ok<int>(default)
-                .WithValue(3);
+                                .WithValue(3);
 
             valueResult = Result.Fail<int>("First error");
 
             valueResult = Result.Fail<int>(new Error("first error"))
-                .WithError("second error");
+                                .WithError("second error");
 
             IEnumerable<Result> results = new List<Result>();
             Result mergedResult = results.Merge();
@@ -89,5 +90,26 @@ public void LogTest()
             var result1 = Result.Ok();
             result1 = result1.Log();
         }
+
+        public async Task BindTests()
+        {
+            var r = Result.Ok(1);
+
+            var r1 = await r.Bind(v => GetVResult())
+                            .Bind(v => GetVResultAsync())
+                            .Bind(v => GetVResult())
+                            .Bind(v => GetVResultAsync())
+                ;
+
+            var r2 = await r.Bind(v => GetVResultAsync());
+        }
+
+        private Result GetResult() => Result.Ok();
+
+        private Result<int> GetVResult() => Result.Ok(1);
+
+        private Task<Result> GetResultAsync() => Task.FromResult(GetResult());
+
+        private Task<Result<int>> GetVResultAsync() => Task.FromResult(GetVResult());
     }
 }