Handle onchange and CanExecute

Author: DerekGooding

README.md

@@ -16,7 +16,7 @@ A lightweight WPF ViewModel framework with automatic source generation that elim
 ### Installation
 
 ```xml
-<PackageReference Include="SimpleViewModel" Version="0.9.5" />
+<PackageReference Include="SimpleViewModel" Version="0.9.6" />
 ```
 
 ### Basic Usage

SimpleViewModel/BindAttribute.cs

@@ -1,4 +1,7 @@
 namespace SimpleViewModel;
 
 [AttributeUsage(AttributeTargets.Field)]
-public sealed class BindAttribute : Attribute;
+public sealed class BindAttribute : Attribute
+{
+    public string? OnChangeMethodName { get; init; }
+}

SimpleViewModel/CommandAttribute.cs

@@ -1,4 +1,7 @@
 namespace SimpleViewModel;
 
 [AttributeUsage(AttributeTargets.Method)]
-public sealed class CommandAttribute : Attribute;
+public sealed class CommandAttribute : Attribute
+{
+    public string? CanExecuteMethodName { get; init; }
+}

SimpleViewModel/SimpleViewModel.csproj

@@ -9,7 +9,7 @@
 
 	  <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
 	  <PackageId>SimpleViewModel</PackageId>
-	  <Version>0.9.5.4</Version>
+	  <Version>0.9.6</Version>
 	  <Authors>Derek Gooding</Authors>
 	  <Company>Derek Gooding</Company>
 	  <Description>

ViewModelGenerator/ViewModelGenerator.cs

@@ -70,7 +70,15 @@ public partial class {className} : BaseViewModel
                 var fieldType = field.Type.ToDisplayString();
                 var fieldName = ToPascal(field.Name);
 
-                viewModelBuilder.AppendLine($"        public {fieldType} {fieldName} {{ get => {field.Name}; set => SetProperty(ref {field.Name}, value); }}");
+                viewModelBuilder.AppendLine(
+$@"        public {fieldType} {fieldName} {{ get => {field.Name}; set 
+                {{
+                    SetProperty(ref {field.Name}, value);");
+
+                var onChange = GetOnChangeMethodName(field);
+                    if (!string.IsNullOrWhiteSpace(onChange))
+                        viewModelBuilder.AppendLine($"   {onChange}();");
+                viewModelBuilder.AppendLine("        }");
             }
 
             foreach (var method in commandMethods)
@@ -101,10 +109,12 @@ public override void Execute(object? parameter)
         {{
             vm.{method.Name}();
         }}
-    }}
-}}
 ");
-
+                    var canExecute = GetCanExecuteMethodName(method);
+                    if(!string.IsNullOrWhiteSpace(canExecute))
+                        viewModelBuilder.AppendLine($"        public override bool CanExecute(object? parameter) => vm.{canExecute}();");
+                    viewModelBuilder.AppendLine("    }");
+                    viewModelBuilder.AppendLine("}");
                     spc.AddSource($"{commandClassName}.g.cs", SourceText.From(commandBuilder.ToString(), Encoding.UTF8));
                 }
 
@@ -122,4 +132,18 @@ private static string ToPascal(string name)
         if (name.StartsWith("_")) name = name.TrimStart('_');
         return char.ToUpperInvariant(name[0]) + name.Substring(1);
     }
+
+    private static string? GetCanExecuteMethodName(IMethodSymbol method)
+    {
+        var attribute = method.GetAttributes().First(x => x.AttributeClass?.Name == "CommandAttribute");
+        var argument = attribute.NamedArguments.First(arg => arg.Key == "CanExecuteMethodName");
+        return argument.Value.Value?.ToString();
+    }
+
+    private static string? GetOnChangeMethodName(IFieldSymbol field)
+    {
+        var attribute = field.GetAttributes().First(x => x.AttributeClass?.Name == "BindAttribute");
+        var argument = attribute.NamedArguments.First(arg => arg.Key == "OnChangeMethodName");
+        return argument.Value.Value?.ToString();
+    }
 }