It turns out that mbgl::AssetFileSource supports absolute file URLs in addition to relative file URLs. So replace the file: scheme with asset: while percent-escaping as necessary. Also added amsterdam.geojson to macos.xcodeproj for consistency with ios.xcodeproj.
Mapbox iOS SDK
A library based on Mapbox GL Native for embedding interactive map views with scalable, customizable vector maps into Cocoa Touch applications on iOS 7.0 and above using Objective-C, Swift, or Interface Builder.
This repository is for day-to-day development of the SDK. Building the SDK yourself requires a number of dependencies and steps that are unnecessary for developing production applications. For production applications, please consider installing an official, prebuilt release instead; see the Mapbox iOS SDK website for installation instructions.
