In some project , in the .xib file , we can see the Placeholders and window at left. But in most recent project i don't see this thing at the left bar. And the window is also strange.
So what's these two names meaning? Are they just the old xcode project organization form?
Directly quoted from https://developer.apple.com.
The nib file may contain placeholder objects that are used to refer to objects that live outside of the document but that may have references to objects in the document, or to which objects in the document may have references. A special placeholder is the File’s Owner.
At runtime, you load a nib file using the method loadNibNamed:owner: or a variant thereof. The File’s Owner is a placeholder in the nib file for the object that you pass as the owner parameter of that method. Whatever connections you establish to and from the File’s Owner in the nib file in Interface Builder are reestablished when you load the file at runtime.
In a nib file, the First Responder is a placeholder object that represents the first object in your application’s dynamically determined responder chain. Because the responder chain of an application cannot be determined at design time, the First Responder placeholder acts as a stand-in target for any action messages that need to be directed at the application’s responder chain.
Read here for more details on Placeholders. You can refer this existing SO ans and this one too.
Hope it helps. Happy Coding!!
