Struct xpcom::interfaces::nsIXPCWrappedJSObjectGetter

#[repr(C)]
pub struct nsIXPCWrappedJSObjectGetter { /* fields omitted */ }

interface nsIXPCWrappedJSObjectGetter : nsISupports

/***************************************************************************/
/**
 * This is a sort of a placeholder interface. It is not intended to be
 * implemented. It exists to give the nsIXPCSecurityManager an iid on
 * which to gate a specific activity in XPConnect.
 *
 * That activity is...
 *
 * When JavaScript code uses a component that is itself implemented in
 * JavaScript then XPConnect will build a wrapper rather than directly
 * expose the JSObject of the component. This allows components implemented
 * in JavaScript to 'look' just like any other xpcom component (from the
 * perspective of the JavaScript caller). This insulates the component from
 * the caller and hides any properties or methods that are not part of the
 * interface as declared in xpidl. Usually this is a good thing.
 *
 * However, in some cases it is useful to allow the JS caller access to the
 * JS component's underlying implementation. In order to facilitate this
 * XPConnect supports the 'wrappedJSObject' property. The caller code can do:
 *
 * // 'foo' is some xpcom component (that might be implemented in JS).
 * try {
 *   var bar = foo.wrappedJSObject;
 *   if(bar) {
 *      // bar is the underlying JSObject. Do stuff with it here.
 *   }
 * } catch(e) {
 *   // security exception?
 * }
 *
 * Recall that 'foo' above is an XPConnect wrapper, not the underlying JS
 * object. The property get "foo.wrappedJSObject" will only succeed if three
 * conditions are met:
 *
 * 1) 'foo' really is an XPConnect wrapper around a JSObject.
 * 2) The underlying JSObject actually implements a "wrappedJSObject"
 *    property that returns a JSObject. This is called by XPConnect. This
 *    restriction allows wrapped objects to only allow access to the underlying
 *    JSObject if they choose to do so. Ususally this just means that 'foo'
 *    would have a property tht looks like:
 *       this.wrappedJSObject = this.
 * 3) The implemementation of nsIXPCSecurityManager (if installed) allows
 *    a property get on the interface below. Although the JSObject need not
 *    implement 'nsIXPCWrappedJSObjectGetter', XPConnect will ask the
 *    security manager if it is OK for the caller to access the only method
 *    in nsIXPCWrappedJSObjectGetter before allowing the activity. This fits
 *    in with the security manager paradigm and makes control over accessing
 *    the property on this interface the control factor for getting the
 *    underlying wrapped JSObject of a JS component from JS code.
 *
 * Notes:
 *
 * a) If 'foo' above were the underlying JSObject and not a wrapper at all,
 *    then this all just works and XPConnect is not part of the picture at all.
 * b) One might ask why 'foo' should not just implement an interface through
 *    which callers might get at the underlying object. There are three reasons:
 *   i)   XPConnect would still have to do magic since JSObject is not a
 *        scriptable type.
 *   ii)  JS Components might use aggregation (like C++ objects) and have
 *        different JSObjects for different interfaces 'within' an aggregate
 *        object. But, using an additional interface only allows returning one
 *        underlying JSObject. However, this allows for the possibility that
 *        each of the aggregte JSObjects could return something different.
 *        Note that one might do: this.wrappedJSObject = someOtherObject;
 *   iii) Avoiding the explicit interface makes it easier for both the caller
 *        and the component.
 *
 *  Anyway, some future implementation of nsIXPCSecurityManager might want
 *  do special processing on 'nsIXPCSecurityManager::CanGetProperty' when
 *  the interface id is that of nsIXPCWrappedJSObjectGetter.
 */

Methods

impl nsIXPCWrappedJSObjectGetter

pub fn coerce<T: nsIXPCWrappedJSObjectGetterCoerce>(&self) -> &T

Cast this nsIXPCWrappedJSObjectGetter to one of its base interfaces.

impl nsIXPCWrappedJSObjectGetter

pub unsafe fn GetNeverCalled(
    &self,
    aNeverCalled: *mut *const nsISupports
) -> nsresult

readonly attribute nsISupports neverCalled;

Methods from Deref<Target = nsISupports>

pub fn coerce<T: nsISupportsCoerce>(&self) -> &T

Cast this nsISupports to one of its base interfaces.

pub unsafe fn QueryInterface(
    &self,
    uuid: &nsIID,
    result: *mut *mut c_void
) -> nsresult

void QueryInterface (in nsIIDRef uuid, [iid_is (uuid), retval] out nsQIResult result);

pub unsafe fn AddRef(&self) -> nsrefcnt

[noscript,notxpcom] nsrefcnt AddRef ();

pub unsafe fn Release(&self) -> nsrefcnt

[noscript,notxpcom] nsrefcnt Release ();

Trait Implementations

impl XpCom for nsIXPCWrappedJSObjectGetter

const IID: nsIID

IID: nsIID = nsID(625717984, 25657, 4564, [143, 224, 0, 16, 164, 231, 61, 154])

fn query_interface<T: XpCom>(&self) -> Option<RefPtr<T>>

Perform a QueryInterface call on this object, attempting to dynamically cast it to the requested interface type. Returns Some(RefPtr) if the cast succeeded, and None otherwise.

impl RefCounted for nsIXPCWrappedJSObjectGetter

unsafe fn addref(&self)

Increment the reference count.

unsafe fn release(&self)

Decrement the reference count, potentially freeing backing memory.

impl Deref for nsIXPCWrappedJSObjectGetter

type Target = nsISupports

The resulting type after dereferencing.

fn deref(&self) -> &nsISupports

Dereferences the value.