UNITY C# - 如何獲取標有自定義屬性（字段）的 class 實例的所有字段？

Question

在 Unity 中，我得到了一個 object 的 class 有很多字段。 其中一些標有 [CockpitControlled] 屬性，我將其定義為：

[AttributeUsage(AttributeTargets.Field)]
public class CockpitControlled : Attribute
{

}

在其他一些 class 中，我想獲得所有這些字段的列表，因為我想更改它們。 問題是如何？

Answer 1

通過反射，您可以獲得一個類型的字段並檢查該屬性是否存在。

例子：

[AttributeUsage(AttributeTargets.Field)]
public class CockpitControlled : Attribute
{
    public int SomeValue { get; set; }
}

public class SomeData
{
    private string _data1;
    [CockpitControlled]
    private string _data2;
    private string _data3;
    [CockpitControlled( SomeValue = 42)]
    private string _data4;
}

static void Main(string[] args)
{
    foreach(var field in typeof(SomeData).GetFields(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic))
    {
        var att = field.GetCustomAttributes(typeof(CockpitControlled), true).FirstOrDefault() as CockpitControlled;
        if(att == null)
        {
            Console.WriteLine($"The field {field.Name} isn't CockpitControlled");
        }
        else
        {
            Console.WriteLine($"The field {field.Name} is CockpitControlled with the value {att.SomeValue}");
        }
    }
}

輸出：

The field _data1 isn't CockpitControlled
The field _data2 is CockpitControlled with the value 0
The field _data3 isn't CockpitControlled
The field _data4 is CockpitControlled with the value 42

編輯：

此示例在 CockpitControlled 的實例字段中設置“bbb”，值為“aaa”：

[AttributeUsage(AttributeTargets.Field)]
public class CockpitControlled : Attribute
{ }

public class SomeData
{
    public string _data1;
    [CockpitControlled]
    public string _data2;
    [CockpitControlled]
    public string _data3;
}

static void Main()
{
    // Create a instance
    var datas = new SomeData { _data1 = "aaa", _data2 = "aaa", _data3 = "zzz",  };
    // For each field of the instance
    foreach (var field in datas.GetType().GetFields(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic))
    {
        // Check if the field is CockpitControlled
        var att = field.GetCustomAttributes(typeof(CockpitControlled), true).FirstOrDefault() as CockpitControlled;
        if (att != null)
        {
            // Get the value of the field
            var curentValue = (string)field.GetValue(datas);
            // If the value of the field equal "aaa"
            if (curentValue == "aaa")
                // Set "bbb"
                field.SetValue(datas, "bbb");
        }
    }

    Console.WriteLine(datas._data1);
    Console.WriteLine(datas._data2);
    Console.WriteLine(datas._data3);
}

結果：

aaa
bbb
zzz