TransientAttribute Class

Definition

Namespace:

ObjCRuntime

Assembly:

Xamarin.iOS.dll

Flags a paramter in an NSObject subclass as being transient.

[System.AttributeUsage(System.AttributeTargets.Parameter, AllowMultiple=false)]
public sealed class TransientAttribute : Attribute

type TransientAttribute = class
    inherit Attribute

Inheritance

Attribute

TransientAttribute

Attributes

AttributeUsageAttribute

Remarks

This attribute is applied to parameters and is only used when transitioning from Objective-C to C#. During those transitions the various Objective-C NSObjects parameters are wrapped into a managed representation of the object.

The runtime will take a reference to the native object and keep the reference until the last managed reference to the object is gone, and the GC has a chance to run.

In a few cases, it is important for the C# runtime to not keep a reference to the native object. This sometimes happens when the underlying native code has attached a special behavior to the lifecycle of the parameter. For example: the destructor for the parameter will perform some cleanup action, or dispose some precious resource.

This attribute informs the runtime that you desire the object to be disposed if possible when returning back to Objective-C from your overwritten method.

The rule is simple: if the runtime had to create a new managed representation from the native object, then at the end of the function, the retain count for the native object will be dropped, and the Handle property of the managed object will be cleared. This means that if you kept a reference to the managed object, that reference will become useless (invoking methods on it will throw an exception).

If the object passed was not created, or if there was already an outstanding managed representation of the object, the forced dispose does not take place.

Constructors

TransientAttribute()

Initializes a new Transient attribute.