ashatora/openlayers
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

Destroyed Implementing formats with ol.format.Format (markdown)

gberaudo
2015-03-31 18:15:26 +02:00
parent 633a2e4092
commit adc74f8066
1 changed files with 0 additions and 21 deletions
Download Patch File Download Diff File Expand all files Collapse all files
Implementing formats with ol.format.Format.md
-21
@@ -1,21 +0,0 @@
`ol.format.Format` defines a number of abstract methods including:
* `readFeatures` returning an `Array.<ol.Feature>`
* `readFeature` returning an `ol.Feature`
* `readGeometry` returning an `ol.geom.Geometry`
Having different functions for multiple return types allows both the user to specify what type of data he wants and for the Compiler to properly type check the code. Depending on the format, it is entirely reasonable to leave one or more of these methods unimplemented, or provide sensible default implementations.
For example, `ol.format.GPX` only supports reading multiple features. Therefore `readFeature` and `readGeometry` are unimplemented and will raise an exception if called.
The IGC format contains only one feature per file, so `readFeature` returns that feature, `readFeatures` returns an array containing a single feature which is the feature in the file, and `readGeometry` is unimplemented.
For formats that only contain a single geometry, like WKB and WKT, `readGeometry` should return that geometry, `readFeature` should return a feature with its geometry set to the geometry read from the file, and `readFeatures` should return an array containing the single feature returned by `readFeature`.
If a file cannot be parsed, then the return value should be `null` for all three cases. Parsing failures should not raise exceptions (although exceptions can be used internally).
## Handling errors
There are an infinite number of ways that data can not meet a specification. It would be an endless battle to try to enumerate and return error messages for each and every single one of them. Formats with multiple features might contain a mix of correctly-formed and malformed features. Should an error be returned in this case?
`ol.format.Format` that it should read as many features as it can, skipping features with any errors.