Basic Examples (5) 

Append a new value to an association at the top level:

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Associate a new value to an existing key, noting that the order of the association is maintained:

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Associate a new value to an existing key at the second level:

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New keys may also be appended at nested levels:

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Nested associations will be created at depth according to the given key specification:

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Scope (1) 

Arbitrary keys are supported:

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Applications (2) 

Starting with an association of contacts, append a new contact as an association at the top level:

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Update an existing value deep in the nested association:

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Properties and Relations (4) 

When appending a new key/value pair, NestedAssociate is equivalent to Append, but with different key syntax:

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NestedAssociate guarantees the order of keys is maintained, whereas Append does not:

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Values can be retrieved from a nested association using resource function NestedLookup:

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Keys can be dropped from a nested association using resource function NestedKeyDrop:

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Possible Issues (4) 

Where keys are themselves lists, they must be wrapped in Key:

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Not wrapping a list-key in Key returns a Failure:

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Where keys are themselves keys, they must be given in the form Key[Key[key]]:

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NestedAssociate strips off the first Key in each key of the key sequence:

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Some built-in functions support this syntax:

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Others do not:

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Avoid this issue by using only strings as keys, and not wrapping keys in Key:

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Where RuleDelayed is used in the given association, NestedAssociate may cause undesired evaluation:

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