NSError Constructors
Definition
Important
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Overloads
| NSError() |
Do not use the Default Constructor unless you are dealing with a low-level API that will initialize the object for you. |
| NSError(NSCoder) |
A constructor that initializes the object from the data stored in the unarchiver object. |
| NSError(NSObjectFlag) |
Constructor to call on derived classes to skip initialization and merely allocate the object. |
| NSError(IntPtr) |
A constructor used when creating managed representations of unmanaged objects; Called by the runtime. |
| NSError(NSString, nint) |
A constructor that initializes the object with a specified domain and an error code. |
| NSError(NSString, nint, NSDictionary) |
NSError()
Do not use the Default Constructor unless you are dealing with a low-level API that will initialize the object for you.
[Foundation.Advice("Always specify a domain and error code when creating an NSError instance")]
public NSError ();- Attributes
Remarks
The default constructor for NSError leaves the object in a partial state that can only be initialized by a handful of low-level Objective-C APIs. In general, you should not use this constructor, you should instead use the constructor that takes an NSString error domain argument.
Applies to
NSError(NSCoder)
A constructor that initializes the object from the data stored in the unarchiver object.
[Foundation.Export("initWithCoder:")]
[ObjCRuntime.DesignatedInitializer]
public NSError (Foundation.NSCoder coder);new Foundation.NSError : Foundation.NSCoder -> Foundation.NSErrorParameters
- coder
- NSCoder
The unarchiver object.
- Attributes
Remarks
This constructor is provided to allow the class to be initialized from an unarchiver (for example, during NIB deserialization). This is part of the NSCoding protocol.
If developers want to create a subclass of this object and continue to support deserialization from an archive, they should implement a constructor with an identical signature: taking a single parameter of type NSCoder and decorate it with the [Export("initWithCoder:"] attribute declaration.
The state of this object can also be serialized by using the companion method, EncodeTo.
Applies to
NSError(NSObjectFlag)
Constructor to call on derived classes to skip initialization and merely allocate the object.
protected NSError (Foundation.NSObjectFlag t);new Foundation.NSError : Foundation.NSObjectFlag -> Foundation.NSErrorParameters
Unused sentinel value, pass NSObjectFlag.Empty.
Remarks
This constructor should be called by derived classes when they completely construct the object in managed code and merely want the runtime to allocate and initialize the NSObject. This is required to implement the two-step initialization process that Objective-C uses, the first step is to perform the object allocation, the second step is to initialize the object. When developers invoke the constructor that takes the NSObjectFlag.Empty they take advantage of a direct path that goes all the way up to NSObject to merely allocate the object's memory and bind the Objective-C and C# objects together. The actual initialization of the object is up to the developer.
This constructor is typically used by the binding generator to allocate the object, but prevent the actual initialization to take place. Once the allocation has taken place, the constructor has to initialize the object. With constructors generated by the binding generator this means that it manually invokes one of the "init" methods to initialize the object.
It is the developer's responsibility to completely initialize the object if they chain up using the NSObjectFlag.Empty path.
In general, if the developer's constructor invokes the NSObjectFlag.Empty base implementation, then it should be calling an Objective-C init method. If this is not the case, developers should instead chain to the proper constructor in their class.
The argument value is ignored and merely ensures that the only code that is executed is the construction phase is the basic NSObject allocation and runtime type registration. Typically the chaining would look like this:
//
// The NSObjectFlag merely allocates the object and registers the
// C# class with the Objective-C runtime if necessary, but no actual
// initXxx method is invoked, that is done later in the constructor
//
// This is taken from Xamarin.iOS's source code:
//
[Export ("initWithFrame:")]
public UIView (System.Drawing.RectangleF frame) : base (NSObjectFlag.Empty)
{
// Invoke the init method now.
var initWithFrame = new Selector ("initWithFrame:").Handle;
if (IsDirectBinding)
Handle = ObjCRuntime.Messaging.IntPtr_objc_msgSend_CGRect (this.Handle, initWithFrame, frame);
else
Handle = ObjCRuntime.Messaging.IntPtr_objc_msgSendSuper_CGRect (this.SuperHandle, initWithFrame, frame);
}
Applies to
NSError(IntPtr)
A constructor used when creating managed representations of unmanaged objects; Called by the runtime.
protected internal NSError (IntPtr handle);new Foundation.NSError : nativeint -> Foundation.NSErrorParameters
- handle
-
IntPtr
nativeint
Pointer (handle) to the unmanaged object.
Remarks
This constructor is invoked by the runtime infrastructure (GetNSObject(IntPtr)) to create a new managed representation for a pointer to an unmanaged Objective-C object. Developers should not invoke this method directly, instead they should call the GetNSObject method as it will prevent two instances of a managed object to point to the same native object.
Applies to
NSError(NSString, nint)
A constructor that initializes the object with a specified domain and an error code.
public NSError (Foundation.NSString domain, nint code);new Foundation.NSError : Foundation.NSString * nint -> Foundation.NSErrorParameters
- domain
- NSString
Error domain
- code
- System.System.IntPtr System.nativeint
Error code.
Applies to
NSError(NSString, nint, NSDictionary)
[Foundation.Export("initWithDomain:code:userInfo:")]
[ObjCRuntime.DesignatedInitializer]
public NSError (Foundation.NSString domain, nint code, Foundation.NSDictionary userInfo);new Foundation.NSError : Foundation.NSString * nint * Foundation.NSDictionary -> Foundation.NSErrorParameters
- domain
- NSString
- code
- System.System.IntPtr System.nativeint
- Attributes