An explanation of the structures and interpretations of the arguments to cloneWithRowsAndSections

react-native-list-view-clone-args.js

// somewhere, you had to set this up
const LVDS = new ListView.DataSource({
	getSectionHeaderData: (blob, sectionId) => blob.sectionData[sectionId],
	getRowData: (blob, sectionId, rowId) => blob.rowData[rowId]
});

// ... and then you had to feed data into it with this:
let newListData = LVDS.cloneWithRowsAndSections(blob, sectionIds, rowIdsBySection)

// but what do blob, sectionIds, and rowIdsBySection look like, and how are they used internally by ListView?
// 
// Imagine that we've got a list of the digits 1-6 and want to present them in two sections: 'Odds' and 'Evens'
// this is what the data would look like that must be fed into cloneWithRowsAndSections



blob = {
	sectionData: {
		// one of these objects for each section; 'evens' and 'odds' are sectionIds
		'evens': { text: '-- The Even Numbers --' },
		'odds': { text: '-- The Odd Numbers --' }
	},
	
	rowData: {
		// one of these objects for each row, 'one' & 'two' are rowIds, etc.
		'one':   { digit: 1, wordLength: 3, name: 'One'   },
		'two':   { digit: 2, wordLength: 3, name: 'Two'   },
		'three': { digit: 3, wordLength: 5, name: 'Three' },
		'four':  { digit: 4, wordLength: 4, name: 'Four'  },
		'five':  { digit: 5, wordLength: 4, name: 'Five'  },
		'six':   { digit: 6, wordLength: 3, name: 'Six'   }
	}
};

// must be fed into cloneWithRowsAndSections
// must contain every sectionId that you wish to display, in display order
sectionIds = [
	'odds',
	'evens'
];

// must be fed into cloneWithRowsAndSections
// each array is a single section's table-of-contents, and lists the rowIds that belong in that section
// this list is cross-referenced with sectionIds (above) by array index, e.g.: when rendering
// the 'evens' section (which has arrayIndex===1), ListView will include the rows named in rowIdsBySection[ 1 ]
rowIdsBySection = [
	[ 'one', 'three', 'five' ],
	[ 'two', 'four', 'six' ]
];