function diffNestedProperty(
updatePayload :? Object,
prevProp, // inferred
nextProp, // inferred
validAttributes : AttributeConfiguration
) : ?Object {
// The style property is a deeply nested element which includes numbers
// to represent static objects. Most of the time, it doesn't change across
// renders, so it's faster to spend the time checking if it is different
// before actually doing the expensive flattening operation in order to
// compute the diff.
if (!styleDiffer(prevProp, nextProp)) {
return updatePayload;
}
// TODO: Walk both props in parallel instead of flattening.
var previousFlattenedStyle = flattenStyle(prevProp);
var nextFlattenedStyle = flattenStyle(nextProp);
if (!previousFlattenedStyle || !nextFlattenedStyle) {
if (nextFlattenedStyle) {
return addProperties(
updatePayload,
nextFlattenedStyle,
validAttributes
);
}
if (previousFlattenedStyle) {
return clearProperties(
updatePayload,
previousFlattenedStyle,
validAttributes
);
}
return updatePayload;
}
// recurse
return diffProperties(
updatePayload,
previousFlattenedStyle,
nextFlattenedStyle,
validAttributes
);
}
computeUpdatedProperties: function(prevProps, nextProps, validAttributes) {
if (__DEV__) {
for (var key in nextProps) {
if (nextProps.hasOwnProperty(key) &&
nextProps[key] &&
validAttributes[key]) {
deepFreezeAndThrowOnMutationInDev(nextProps[key]);
}
}
}
var updatePayload = diffRawProperties(
null, // updatePayload
prevProps,
nextProps,
validAttributes
);
// The style property is a deeply nested element which includes numbers
// to represent static objects. Most of the time, it doesn't change across
// renders, so it's faster to spend the time checking if it is different
// before actually doing the expensive flattening operation in order to
// compute the diff.
if (styleDiffer(nextProps.style, prevProps.style)) {
var nextFlattenedStyle = precomputeStyle(flattenStyle(nextProps.style));
updatePayload = diffRawProperties(
updatePayload,
this.previousFlattenedStyle,
nextFlattenedStyle,
ReactNativeStyleAttributes
);
this.previousFlattenedStyle = nextFlattenedStyle;
}
return updatePayload;
},