Often we query an object and need to create a map out of the list of records retrieved. The most straightforward way is to declare a Map<ID, sObject> and initialize it with a\u00a0list resulting from a\u00a0SOQL query.<\/p>\n
List<Account> acctList = [ SELECT ID, Name, AccountNumber
\n FROM Account ];<\/p>\nMap<ID, Account> acctMapByID = new\u00a0Map<ID, Account>( acctList );<\/p><\/blockquote>\n
The code shown above will populate the acctMapByID with accounts using their IDs<\/strong> as the key.<\/p>\n
However, what if we wanted to create a map indexed by AccountNumber instead<\/strong>? We would have to loop through the list and add the records to the map one by one specifying theAccountNumber as the key.<\/p>\n
List<Account> acctList = [ SELECT ID, Name, AccountNumber
\n FROM Account ];<\/p>\nMap<String, Account> acctMapByNumber =
\n new\u00a0Map<String, Account>();<\/p>\nfor( Account anAccount : acctList ) {
\n acctMapByNumber.put( anAccount.AccountNumber, anAccount );
\n}<\/p><\/blockquote>\nNow what if there was\u00a0a way to do that without any loops and in a single line of code?<\/p>\n
Map<String, SObject> acctMapByNumber\u00a0=
\n MapCreator.createMapByIndex( acctList, 'AccountNumber' );<\/code><\/p><\/blockquote>\nBelow is the definition of the MapCreator class<\/strong> that allows that.<\/p>\n
public class MapCreator {
\n public static Map<String, SObject> createMapByIndex(
\n List<SObject> aList, String indexField ) {<\/p>\n\/\/ get the list in JSON format
\n String jsonList = JSON.serialize( aList );<\/p>\n\/\/ remove enclosing []
\n jsonList = jsonList.substring( 1, jsonList.length() - 1 );<\/p>\n\/\/ copy the indexField value in front of each
\n \/\/ {} group using RegEx substitution
\n \/\/ example result: value:{...\"indexField\":\"value\"...}
\n jsonList = '{' + jsonList.replaceAll(
\n '(\\\\{.*?\"' + indexField + '\":\"(.*?)\"(,\".*?\")*\\\\},?)'
\n , '\"$2\":$1' ) + '}';<\/p>\n\/\/ create map from the modified JSON
\n Map<String, SObject> changedMap =
\n (Map<String, SObject>) JSON.deserialize(
\n jsonList, Map<String, SObject>.class );<\/p>\nreturn changedMap;
\n }<\/p>\n}<\/code><\/p><\/blockquote>\n
It first converts the list to a JSON string, then modifies the string to look as if it was a serialized Map. It does that by using RegEx to insert the index in front of each record in the string. It then deserializes the modified JSON string into a map.
\nIt doesn’t use any loops explicitly although there must be loops hidden in the RegEx and JSON method internal implementations, which are much faster. <\/p>\nWhat would be the advantages of using this class instead of coding the loop?<\/p>\n
The\u00a0MapCreator class<\/strong> uses string replacement\/RegEx, which is faster than looping and creating map elements one by one.<\/p>\n
According to my tests, it runs faster than looping for lists of roughly 8 records or more. For 63 records, it should be 5 to 6 times faster depending on the size of the records.<\/p>\n
It might not be relevant for most of the situations but if you have a long running code that needs to be optimized, it might be worth a try.<\/p>\n
PS.:<\/strong> I fixed a problem with the way WordPress displays code that made it convert quotes and double-quotes to special characters. Now the code can be copied and pasted onto Salesforce.
\n <\/p>\n","protected":false},"excerpt":{"rendered":"Often we query an object and need to create a map out of the list of records retrieved. The most straightforward way is to declare a Map<ID, sObject> and initialize it with a\u00a0list resulting from a\u00a0SOQL query. List<Account> acctList = [ SELECT ID, Name, AccountNumber FROM Account ]; Map<ID, Account> acctMapByID = new\u00a0Map<ID, Account>( acctList […]<\/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-180","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\/180","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=180"}],"version-history":[{"count":0,"href":"https:\/\/blog.felineflock.com\/index.php\/wp-json\/wp\/v2\/posts\/180\/revisions"}],"wp:attachment":[{"href":"https:\/\/blog.felineflock.com\/index.php\/wp-json\/wp\/v2\/media?parent=180"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.felineflock.com\/index.php\/wp-json\/wp\/v2\/categories?post=180"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.felineflock.com\/index.php\/wp-json\/wp\/v2\/tags?post=180"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}