Create informational popup / tooltip in Cocoa

The question title is kind of vague, but I really don't know what the thing is called.

I am trying to create one of those yellow informational popup t开发者_开发百科hings. Anyone can tell me what they're called and how I can create them?

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That's called a tool tip. You can set the tool tip for any NSView using setToolTip:.

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If you are using NSTextView, you can even set an attribute for a certain range in NSTextstorage, that displays the Tooltip. Something like:

[textStorage addAttribute:NSToolTipAttributeName
                    value:error.description
                    range:range];