Question

I type NSLog, and it display NSLog(id, ...), and it shows some kind of tips for me in the editor, when I copy the text to the TextEdit, it shows that it is NSLog(<#id, ...#>), so, I tried to type NSLog(<#id, ...#>) manually, but it can’t shows the tips like the first line. How did XCode handle that? Thanks.

Answer 1

It handles it by replacing <#sometext#> with the blue bubble placeholder, as you quite discovered, but this does not affect the case when you type it yourself directly in the Xcode editor (because it does not have any sense to type this in the code directly, you would generally instead type the real content there).

If you type some code that contains <#sometext#> in TextEdit, then you copy/paste it back in the Xcode editor, Xcode will insert the blue bubbles as placeholders where you have typed <#...#> in your text.

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One usage of this is to generate Code Snippets. Simply select some piece of code in your Xcode Editor, then drag & drop it in the Code Snippet Library; you will then be able to drag & drop it back in your Code Editor later to reuse this same piece of code. If this Code Snippet contains some <#placeholder#> Xcode will then insert blue bubbles at this position.
For more information, see this page in the documentation that contains a nice video that explains it in details.