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filter-paths.md

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Filter paths options

Observable.observe(...) allows options parameter, third one, optional.

Some of the options are filtering ones, allowing to specify the changes of interest from within the observable graph. Here is a detailed description of those options.

pathsFrom

Value expected to be a non-empty string representing a path, any changes of which and deeper will be delivered to the observer.

This option MAY NOT be used together with path option.

Given, that we have subscribed for the changes via: 
Observable.observe(o, callback, { pathsFrom: 'address' });
Following mutations will be delivered to the callback: 
o.address.street.apt = 5;
o.address.city = 'DreamCity';
o.address = {};
Following mutations will not be delivered to the callback: 
o.lastName = 'Joker';

pathsOf

Value expected to be a string, which MAY be empty, representing a path. Changes to direct properties of which will be notified.

Given, that we have subscribed for the changes via: 
Observable.observe(o, callback, { pathsOf: 'address' });
Following mutations will be delivered to the callback: 
o.address.street = {};
o.address.city = 'DreamCity';
Following mutations will not be delivered to the callback: 
o.lastName = 'Joker';
o.address = {};
o.address.street.apt = 5;

path

Value expected to be a non-empty string, representing a specific path to observe. Only a changes of this exact path will be notified.

Given, that we have subscribed for the changes via: 
Observable.observe(o, callback, { path: 'address.street' });
Following mutations will be delivered to the callback: 
o.address.street = {};
Following mutations will not be delivered to the callback: 
o.lastName = 'Joker';
o.address = {};
o.address.street.apt = 5;