91 lines
3.2 KiB
Markdown
91 lines
3.2 KiB
Markdown
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# MapTo
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[](https://www.nuget.org/packages/MapTo/)
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A convention based object to object mapper using [Roslyn source generator](https://github.com/dotnet/roslyn/blob/master/docs/features/source-generators.md).
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MapTo is a library to programmatically generate the necessary code to map one object to another during compile-time, eliminating the need to use reflection to map objects and make it much faster in runtime. It provides compile-time safety checks and ease of use by leveraging extension methods.
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## Installation
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```
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dotnet add package MapTo --prerelease
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```
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## Usage
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MapTo relies on a set of attributes to instruct it on how to generate the mappings. To start, declare the destination class as `partial` and annotate it with `MapFrom` attribute. As its name implies, `MapFrom` attribute tells the library what the source class you want to map from is.
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```c#
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using MapTo;
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namespace App.ViewModels
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{
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[MapFrom(typeof(App.Data.Models.User))]
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public partial class UserViewModel
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{
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public string FirstName { get; }
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public string LastName { get; }
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[IgnoreProperty]
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public string FullName { get; set; }
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}
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}
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```
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To get an instance of `UserViewModel` from the `User` class, you can use any of the following methods:
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```c#
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var user = new User(id: 10) { FirstName = "John", LastName = "Doe" };
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var vm = user.ToUserViewModel(); // A generated extension method for User class.
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// OR
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vm = new UserViewModel(user); // A generated contructor.
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// OR
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vm = UserViewModel.From(user); // A generated factory method.
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```
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> Please refer to [sample console app](https://github.com/mrtaikandi/MapTo/tree/master/test/TestConsoleApp) for a more complete example.
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## Available Attributes
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### IgnoreProperty
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By default, MapTo will include all properties with the same name (case-sensitive), whether read-only or not, in the mapping unless annotating them with the `IgnoreProperty` attribute.
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```c#
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[IgnoreProperty]
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public string FullName { get; set; }
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```
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### MapProperty
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This attribute gives you more control over the way the annotated property should get mapped. For instance, if the annotated property should use a property in the source class with a different name.
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```c#
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[MapProperty(SourcePropertyName = "Id")]
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public int Key { get; set; }
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```
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### MapTypeConverter
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A compilation error gets raised by default if the source and destination properties types are not implicitly convertible, but to convert the incompatible source type to the desired destination type, `MapTypeConverter` can be used.
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This attribute will accept a type that implements `ITypeConverter<in TSource, out TDestination>` interface.
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```c#
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[MapFrom(typeof(User))]
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public partial class UserViewModel
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{
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public DateTimeOffset RegisteredAt { get; set; }
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[IgnoreProperty]
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public ProfileViewModel Profile { get; set; }
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[MapTypeConverter(typeof(IdConverter))]
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[MapProperty(SourcePropertyName = nameof(User.Id))]
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public string Key { get; }
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private class IdConverter : ITypeConverter<int, string>
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{
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public string Convert(int source, object[] converterParameters) => $"{source:X}";
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}
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}
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```
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