record

来源： https://stackoverflow.com/questions/63667281/associate-a-function-with-a-type-in-haskell

来源： https://stackoverflow.com/questions/63667281/associate-a-function-with-a-type-in-haskell

问题 I have a data structure like below: Products | name | region_ids | ---------------------------------- | shoe | c32, a43, x53 | | hat | c32, f42 | # Schema name STRING NULLABLE region_ids RECORD REPEATED region_ids.value STRING NULLABLE Regions | _id | name | --------------------- | c32 | london | | a43 | manchester | | x53 | bristol | | f42 | liverpool | # Schema _id STRING NULLABLE name STRING NULLABLE I want to look up the array of "region_ids" and replace them by the region name to result

问题 Suppose type pair_int = {l1:int; l2:int, ..., ln:int} let test = {l1=2; l2=4, ..., ln=71} I thought I could do something like map (fun (x,y) -> y) test , but it doesn't work How can I get the list [2,4, ..., 71] from test ? 回答1: There's no nice way to do this inside the OCaml type system. You can't map over the fields of a record because they can be of all different types. Your type pair_int looks suspiciously like a list or an array already. The field names don't add any semantic content,

问题 I would like to implement my own RecordMapper and use Mapstruct to map the Record to the POJO. I don't quite understand how to accomplish this. I followed this part of the docs: https://www.jooq.org/doc/3.13/manual/sql-execution/fetching/pojos-with-recordmapper-provider/ My mapper looks like this: public class LanguageMapper<R extends Record, E> implements RecordMapper<R, Language> { @Override public Language map(R record) { LanguageRecord languageRecord = (LanguageRecord) record; // this is

问题 When I generate the JOOQ POJOs, the constructor follows the same order for the parameters as the fields in the database table. When querying the table and using fetchInto this works fine, as long as the order of the POJO constructor parameters and the order of the fields in the database table are the same. return create .select() .from(KEY) .fetchInto(Key.class); How can I map the query above into Key.class regardless of the constructor parameter order? E.g. can I use something like mapstruct

问题 When I generate the JOOQ POJOs, the constructor follows the same order for the parameters as the fields in the database table. When querying the table and using fetchInto this works fine, as long as the order of the POJO constructor parameters and the order of the fields in the database table are the same. return create .select() .from(KEY) .fetchInto(Key.class); How can I map the query above into Key.class regardless of the constructor parameter order? E.g. can I use something like mapstruct

问题 I need to mix "record" type with null type in Schema. "name":"specShape", "type":{ "type":"record", "name":"noSpecShape", "fields":[ { "name":"bpSsc", "type":"null", "default":null, "doc":"SampleValue: null" },... For example, for some datas specShape may be null. So if I set type to "name":"specShape", "type":{ **"type":["record", "null"],** "name":"noSpecShape", "fields":[ { "name":"bpSsc", "type":"null", "default":null, "doc":"SampleValue: null" },... it says No type: {"type":["record",

问题 I need to mix "record" type with null type in Schema. "name":"specShape", "type":{ "type":"record", "name":"noSpecShape", "fields":[ { "name":"bpSsc", "type":"null", "default":null, "doc":"SampleValue: null" },... For example, for some datas specShape may be null. So if I set type to "name":"specShape", "type":{ **"type":["record", "null"],** "name":"noSpecShape", "fields":[ { "name":"bpSsc", "type":"null", "default":null, "doc":"SampleValue: null" },... it says No type: {"type":["record",

问题 I need to mix "record" type with null type in Schema. "name":"specShape", "type":{ "type":"record", "name":"noSpecShape", "fields":[ { "name":"bpSsc", "type":"null", "default":null, "doc":"SampleValue: null" },... For example, for some datas specShape may be null. So if I set type to "name":"specShape", "type":{ **"type":["record", "null"],** "name":"noSpecShape", "fields":[ { "name":"bpSsc", "type":"null", "default":null, "doc":"SampleValue: null" },... it says No type: {"type":["record",