README
¶
query-go
This is a Go package to extract value by a query string like key[0].key["key"].
See usage and example in GoDoc.
Basic Usage
ParseString parses a query string and returns the query which extracts the value.
q, err := query.ParseString(`key[0].key["key"]`)
v, err := q.Extract(target)
Query Syntax
The query syntax understood by this package when parsing is as follows.
.key extracts by a key of map or field name of struct ("." can be omitted if the head of query)
[0] extracts by a index of array or slice
["key"] same as the ".key"
Documentation
¶
Overview ¶
Package query provides to extract the element from a value.
ParseString parses a query string and returns the query which extracts the value.
q, err := query.ParseString(`key[0].key["key"]`) v, err := q.Extract(target)
Query Syntax ¶
The query syntax understood by this package when parsing is as follows.
.key extracts by a key of map or field name of struct ("." can be omitted if the head of query)
[0] extracts by a index of array or slice
["key"] same as the ".key"
Index ¶
Examples ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
This section is empty.
Types ¶
type Index ¶
type Index struct {
// contains filtered or unexported fields
}
Index represents an extractor to access the value by index.
type IndexExtractor ¶
IndexExtractor is the interface that wraps the ExtractByIndex method.
ExtractByIndex extracts the value by index. It reports whether the index is found and returns the found value.
type Key ¶
type Key struct {
// contains filtered or unexported fields
}
Key represents an extractor to access the value by key.
type KeyExtractor ¶
KeyExtractor is the interface that wraps the ExtractByKey method.
ExtractByKey extracts the value by key. It reports whether the key is found and returns the found value.
Example ¶
package main
import (
"fmt"
"github.com/zoncoen/query-go"
)
type orderedMap struct {
elems []*elem
}
type elem struct {
k, v interface{}
}
func (m *orderedMap) ExtractByKey(key string) (interface{}, bool) {
for _, e := range m.elems {
if k, ok := e.k.(string); ok {
if k == key {
return e.v, true
}
}
}
return nil, false
}
func main() {
q := query.New().Key("key")
v, _ := q.Extract(&orderedMap{
elems: []*elem{{k: "key", v: "value"}},
})
fmt.Println(v)
}
Output: value
type Option ¶
type Option func(*Query)
Option represents an option for Query.
func CustomStructFieldNameGetter ¶
func CustomStructFieldNameGetter(f func(f reflect.StructField) string) Option
CustomStructFieldNameGetter returns the Option to set f as custom function which gets struct field name. f is called by Key.Extract to get struct field name, if the target value is a struct.
Example ¶
package main
import (
"fmt"
"reflect"
"strings"
"github.com/zoncoen/query-go"
)
// Person represents a person.
type Person struct {
Name string `json:"name,omitempty"`
}
// getFieldNameByJSONTag returns the JSON field tag as field name if exists.
func getFieldNameByJSONTag(field reflect.StructField) string {
tag, ok := field.Tag.Lookup("json")
if ok {
strs := strings.Split(tag, ",")
return strs[0]
}
return field.Name
}
func main() {
person := Person{
Name: "Alice",
}
q := query.New(
query.CustomStructFieldNameGetter(getFieldNameByJSONTag),
).Key("name")
name, _ := q.Extract(person)
fmt.Println(name)
}
Output: Alice
type Query ¶
type Query struct {
// contains filtered or unexported fields
}
Query represents a query to extract the element from a value.
func ParseString ¶
ParseString parses a query string s and returns the corresponding Query.
Example ¶
package main
import (
"fmt"
"github.com/zoncoen/query-go"
)
type S struct {
Maps []map[string]string
}
func main() {
q, err := query.ParseString("Maps[0].key")
if err == nil {
v, _ := q.Extract(&S{
Maps: []map[string]string{
{"key": "value"},
},
})
fmt.Println(v)
}
}
Output: value
func (*Query) Extractors ¶ added in v1.1.0
Extractors returns query extractors of q.
Source Files
Directories
¶
| Path | Synopsis |
|---|---|
|
Package ast declares the types used to represent syntax trees.
|
Package ast declares the types used to represent syntax trees. |
|
extractor
|
|
|
protobuf
module
|
|
|
yaml
module
|
|
|
Package parser implements a parser for a query string.
|
Package parser implements a parser for a query string. |
|
Package token defines constants representing the lexical tokens.
|
Package token defines constants representing the lexical tokens. |