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Line 1: − ===Reflection===+ − SMAPI provides an API for robustly accessing fields, properties, or methods you otherwise couldn't access, such as private fields. You can use it from <tt>helper.Reflection</tt> in your entry method, or <tt>this.Helper.Reflection</tt> elsewhere in your entry class. − Here are a few examples of what this lets you do:+ + + + + + + + + + + + + + + + + + + + + + + + + + − + + + + + + + + + − + + + + + + + + + + − + − if(Game1.currentLocation is MineShaft)+ − this.Helper.Reflection.GetField<Random>(Game1.currentLocation, "mineRandom").SetValue(new Random());+ + + + − This works with static or instance fields/methods, caches the reflection to improve performance, and will throw useful errors automatically when reflection fails.+ − + − − + +
Modding:Modder Guide/APIs/Reflection (view source)
Revision as of 05:28, 28 May 2018
, 05:28, 28 May 2018expand
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{{../../header}}
The reflection API lets you access fields, properties, or methods you otherwise couldn't access. You can use it from <tt>helper.Reflection</tt> in your entry method, or <tt>this.Helper.Reflection</tt> elsewhere in your entry class.
==Intro==
[https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/concepts/reflection ''Reflection''] is a powerful C# feature which lets code analyse and interact with code. SMAPI provides a simplified reflection API focused on accessing private game fields, properties, and methods. SMAPI will automatically handle validation, caching, and performance optimisation.
==Basic reflection==
===Overview===
SMAPI provides three overloaded methods to access code: <tt>GetField</tt>, <tt>GetProperty</tt>, and <tt>GetMethod</tt>. Each one takes three arguments:
{| class="wikitable"
|-
! argument
! purpose
|-
| <tt>obj</tt> or <tt>type</tt>
| The instance (or type if static) which has the private field/property/method you want to access.
|-
| <tt>name</tt>
| The name of the private field/property/method.
|-
| <tt>required</tt>
| Whether to throw a descriptive exception if the field/property/method isn't found. Default true. If set to false, it will return <tt>null</tt> instead and you should validate it yourself.
|}
Each method returns an object you can use to interact further with it — like getting or setting the field/property value, or invoking the method.
===Fields and properties===
<tt>GetField</tt> and <tt>GetProperty</tt> are used the same way. Both return an object with two methods: <tt>GetValue</tt> returns the current field/property value, and <tt>SetValue</tt> overrides their value.
You can get the value directly:
<source lang="c#">
<source lang="c#">
// did you pet your pet today?
// get value of instance field
bool wasPet = this.Helper.Reflection.GetField<bool>(pet, "wasPetToday").GetValue();
bool wasPet = this.Helper.Reflection.GetField<bool>(pet, "wasPetToday").GetValue();
</source>
Or you can keep a reference to the reflection data, and change the value separately:
<source lang="c#">
// set value of static field
IReflectedField<int> soundTimer = this.Helper.Reflection.GetField<int>(typeof(Junimo), "soundTimer");
soundTimer.SetValue(100);
</source>
// what is the spirit forecast today?
If you need to access the field/property repeatedly, keeping the reflection object will improve performance.
===Methods===
<tt>GetMethod</tt> returns an object with one overloaded method. The <tt>Invoke</tt> comes in two forms:
* <tt>Invoke()</tt> calls a method with no return value.
* <tt>Invoke<T>()</tt> calls a method which returns a value, where <tt>T</tt> is the expected return type.
For example, this calls the private <tt>TV.getFortuneForecast</tt> method and stores the value it returns:
<source lang="c#">
string forecast = this.Helper.Reflection
string forecast = this.Helper.Reflection
.GetMethod(new TV(), "getFortuneForecast")
.GetMethod(new TV(), "getFortuneForecast")
.Invoke<string>();
.Invoke<string>();
</source>
// randomise the mines
If the method expects arguments, you can just add those to the <tt>Invoke</tt> method:
<source lang="c#">
Vector2 spawnTile = new Vector2(25, 25);
this.helper.Reflection
.GetMethod(Game1.getFarm(), "doSpawnCrow")
.Invoke(spawnTile);
</source>
</source>
==Advanced reflection==
If you need to do more, you can access the underlying C# reflection types:
If you need to do more, you can switch to [https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/concepts/reflection C#'s underlying reflection API]:
<source lang="c#">
<source lang="c#">
FieldInfo field = this.Helper.Reflection.GetField<string>(…).FieldInfo;
FieldInfo field = this.Helper.Reflection.GetField<string>(…).FieldInfo;
MethodInfo method = this.Helper.Reflection.GetMethod(…).MethodInfo;
MethodInfo method = this.Helper.Reflection.GetMethod(…).MethodInfo;
</source>
</source>
Or even use [https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/concepts/reflection C# reflection] directly. Note that SMAPI adds caching and optimisations which you'll need to handle yourself if you do this.