{"id":211,"date":"2014-12-30T10:42:03","date_gmt":"2014-12-30T05:42:03","guid":{"rendered":"http:\/\/learnsf.wordpress.com\/?p=211"},"modified":"2014-12-30T10:42:03","modified_gmt":"2014-12-30T05:42:03","slug":"another-trick-how-to-obtain-a-set-from-any-field-in-a-list-faster-and-without-loops","status":"publish","type":"post","link":"https:\/\/blog.felineflock.com\/index.php\/2014\/12\/30\/another-trick-how-to-obtain-a-set-from-any-field-in-a-list-faster-and-without-loops\/","title":{"rendered":"Another trick: how to obtain a set from any field in a list – faster and without loops!"},"content":{"rendered":"

This is like the previous post about getting maps out of a list<\/a>, but with the same trick applied for getting a set. <\/p>\n

In triggers, we usually code a loop like below to collect certain IDs in a set and later use the set in a query.<\/p>\n

…
\nSet<String> acctIDSet = new Set<String>();
\nfor( Contact aContact : trigger.new ) {
\n    acctIDSet.add( aContact.AccountID );
\n}
\n…\n<\/p><\/blockquote>\n

The new SetCreator class<\/strong> does that without any loops and in a single line of code.<\/p>\n

Set<String> acctIDSet =
\n      SetCreator.createSetFromField( trigger.new, ‘AccountID’ );<\/p><\/blockquote>\n

Below is the definition of the SetCreator class<\/strong> that allows that.<\/p>\n

public class SetCreator {
\n    public static Set<String> createSetFromField(
\n        List<SObject> aList, String fieldName ) {<\/p>\n

    \/\/ get the list in JSON format
\n    String jsonList = JSON.serialize( aList );<\/p>\n

    \/\/ copy only the fieldName value using RegEx substitution
\n    jsonList = jsonList.replaceAll(
\n        '(\\\\{.*?\"' + fieldName + '\":\"(.*?)\"(,\".*?\")*\\\\},?)'
\n        , ',\"$2\"' ).replace( '[,', '[' );<\/p>\n

    \/\/ create set from the modified JSON
\n    Set<String> extractedSet =
\n        (Set<String>) JSON.deserialize(
\n            jsonList, Set<String>.class );<\/p>\n

    return extractedSet;
\n    }<\/p>\n

}<\/code><\/p><\/blockquote>\n

It converts the list to a JSON string and modifies the string to look as if it was a serialized Set. It uses RegEx to keep the specified field values and remove everything else. It then deserializes the modified JSON string into a Set.
\nAgain, there are no explicit loops – all of them are internal to the RegEx\/JSON implementations, and are much faster. <\/p>\n

Even if there are duplicates, they are automatically eliminated during the deserialization of the JSON string.<\/p>\n

 <\/p>\n","protected":false},"excerpt":{"rendered":"

This is like the previous post about getting maps out of a list, but with the same trick applied for getting a set. In triggers, we usually code a loop like below to collect certain IDs in a set and later use the set in a query. … Set<String> acctIDSet = new Set<String>(); for( Contact aContact […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"_uf_show_specific_survey":0,"_uf_disable_surveys":false,"footnotes":""},"categories":[13],"tags":[],"class_list":["post-211","post","type-post","status-publish","format-standard","hentry","category-no-category"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/blog.felineflock.com\/index.php\/wp-json\/wp\/v2\/posts\/211","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blog.felineflock.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.felineflock.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.felineflock.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.felineflock.com\/index.php\/wp-json\/wp\/v2\/comments?post=211"}],"version-history":[{"count":0,"href":"https:\/\/blog.felineflock.com\/index.php\/wp-json\/wp\/v2\/posts\/211\/revisions"}],"wp:attachment":[{"href":"https:\/\/blog.felineflock.com\/index.php\/wp-json\/wp\/v2\/media?parent=211"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.felineflock.com\/index.php\/wp-json\/wp\/v2\/categories?post=211"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.felineflock.com\/index.php\/wp-json\/wp\/v2\/tags?post=211"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}