MapCacheConfig

Each time a tile is going to be retrieved from the server its x,y and z (zoom) values are plugged into this URL template.

Default value "https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png

Where

1. {s} Replaced with one of the subdomains defined in subdomains.
2. {z} Replaced with the zoom level value.
3. {x} Replaced with the position of the tile in the X asis for this zoom level
4. {y} Replaced with the position of the tile in the X asis for this zoom level

Subdomains used on the urlTemplate

It must be smaller or equal than maximumZ

Default value is 0.

Maximum supported zoom by the tile server

Tiles with a z zoom beyond maximumZ supported by the tile server will return a HTTP 404 error.

Values vary from server to server. For example OpenStreetMap supports 19, but OpenCycleMap supports 22. The maximum value that can be set is TileCoords.maxZoom (25).

Default value: 19. If 0 or negative is set iOS default value (i.e. 21).

If set to true when zooming in beyond maximumZ the tiles at maximumZ will be upsampled and shown. This mitigates the issue of showing an empty map when zooming in beyond maximumZ.

maximumZ is vital to zoom working, make sure it is properly set.

Name of the cache A folder will be created with this name all files will be stored in that folder

This is useful if you want to have different caches for different purposes as well as use the same MapCache in different parts of your application.

Default value “MapCache”

Cache capacity in bytes. When the cache exceeds this size, the least recently used tiles are deleted. By default is infinite (i.e. UINT64_MAX).

Optional custom base URL for the cache directory.

When set, overrides the default temporary NSCachesDirectory/DiskCache/ path. Useful for permanent storage, for example pointing to applicationSupportDirectory.

Default is nil, which uses the default temporary cache location (DiskCache.defaultBaseURL()).

Example usage:

let appSupport = FileManager.default.urls(for: .applicationSupportDirectory, in: .userDomainMask).first!
config.baseURL = appSupport.appendingPathComponent("MapCacheTiles", isDirectory: true)

Tile size of the tile. Default is 256x256

Load tile mode. Sets the strategy to be used when loading a tile. By default loads from the cache and if it fails loads from the server

Constructor with all the default values.

Constructor that overwrites the urlTemplate`

Selects one of the subdomains randomly.

Keeps track of the index of the last subdomain requested for round robin

Round Robin algorithm If subdomains are a,b,c then it makes requests to a,b,c,a,b,c,a,b,c…

It uniformly makes requests to all the subdomains.