I have a sketch prototyp file and want to export all icons with different size for iOS/Xcode. How should I do? I only know how to export an icon/image with different size, but no idea what about for all icons or images. Maybe Sketch does not support this function?
Welcome to Stack Exchange!
Selecting all the icons you want to export and then make them exportable (right panel) can do the trick.
Here's a gif of me exporting three icons to three different PNG files.
(sorry for the gif quality, a higher version can be viewed here (webm) : https://giant.gfycat.com/PeacefulShyJackal.webm
After a second look at your question, I realize I did not answer at all since you wanted different sizes for your files.
To export your icons with different sizes, you can add a new export option thanks to the "+" icon (see image).
You can then export all your icons with your export choices, here's the final result in my finder:
After slicing them with right preset (iOS in your case), you can also use this icon in the corner to export them in batch.
