| Portability | portable |
|---|---|
| Stability | experimental |
| Maintainer | Chris Done <chrisdone@gmail.com> |
| Safe Haskell | None |
Database.PostgreSQL.Simple.QueryResults
Description
The QueryResults typeclass, for converting a row of results
returned by a SQL query into a more useful Haskell representation.
Predefined instances are provided for tuples containing up to ten elements.
- class QueryResults a where
- convertResults :: [Field] -> [Maybe ByteString] -> a
- convertError :: [Field] -> [Maybe ByteString] -> Int -> a
Documentation
class QueryResults a whereSource
Methods
convertResults :: [Field] -> [Maybe ByteString] -> aSource
Convert values from a row into a Haskell collection.
This function will throw a ResultError if conversion of the
collection fails.
Instances
| Result a => QueryResults (Only a) | |
| (Result a, Result b) => QueryResults (a, b) | |
| (Result a, Result b, Result c) => QueryResults (a, b, c) | |
| (Result a, Result b, Result c, Result d) => QueryResults (a, b, c, d) | |
| (Result a, Result b, Result c, Result d, Result e) => QueryResults (a, b, c, d, e) | |
| (Result a, Result b, Result c, Result d, Result e, Result f) => QueryResults (a, b, c, d, e, f) | |
| (Result a, Result b, Result c, Result d, Result e, Result f, Result g) => QueryResults (a, b, c, d, e, f, g) | |
| (Result a, Result b, Result c, Result d, Result e, Result f, Result g, Result h) => QueryResults (a, b, c, d, e, f, g, h) | |
| (Result a, Result b, Result c, Result d, Result e, Result f, Result g, Result h, Result i) => QueryResults (a, b, c, d, e, f, g, h, i) | |
| (Result a, Result b, Result c, Result d, Result e, Result f, Result g, Result h, Result i, Result j) => QueryResults (a, b, c, d, e, f, g, h, i, j) |
convertError :: [Field] -> [Maybe ByteString] -> Int -> aSource
Throw a ConversionFailed exception, indicating a mismatch
between the number of columns in the Field and row, and the
number in the collection to be converted to.