Added inheritance for StyleSheet.

[lukasredev]

In my current project I have a iOS application, where the user can switch between an edit and a normal view. Edit and normal view are displayed by the same component but with different styles. Only a few styles differ between the two states. That's why I though it would be really nice, if one had some sort of inhertiance for the styles.

Current Code

var styles = StyleSheet.create( {
  viewStyle: {
    marginTop: 5,
    marginBottom: 5,
    backgroundColor: '#bbbbbb',
    flex: 1
  },
  viewStyleEdit: {
    marginTop: 20,
    marginBottom: 5,
    backgroundColor: '#fffffff',
    flex: 1
  }
});

Proposal

var styles = StyleSheet.create( {
  viewStyle: {
    marginTop: 5,
    marginBottom: 5,
    backgroundColor: '#bbbbbb',
    flex: 1
  },
  viewStyleEdit: ["viewStyle". {
    marginTop: 20,
    backgroundColor: '#fffffff'
  } ]
});

The StyleSheetInheritance module I wrote, merges all values from the "viewStyle" into the "viewStyleEdit" object.

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