Golang notes (1)-database query results mapped to struct

Common mapping mode

Query:="Selectfromuserwhere id=?"

A single structural body
ret:=&activity{}dbclient (). Find (Query,activityid). Unique (ret)
struct array
Ret:=[]activity{}

Dbclient (). Find (Query,activityid). List (&ret)

1. Define the structure body

struct {id Int64 ' col: 'ID' json:'ID'string ' col: 'name' JSON:'name' '}

2. Defining Database Objects

struct {    data       []map[string]string//    err        error                 exception }var prokdb *sql. Db

3. Pass the object address to the struct

Func (d *dao) Unique (inch Interface{}) error {ifLen (D.data) >0 {returnD.mapping (d.data[0], reflect. ValueOf (inch))}returnNil}func (d*dao) mapping (M map[string]string, v reflect. Value) Error {t:=V.type () Val:=V.elem () Typ:=T.elem ()if!val. IsValid () {returnErrors. New ("data type is incorrect")} forI: =0; I < Val. Numfield (); i++{value:=val. Field (i) Kind:=value. Kind () Tag:= Typ. Field (i). Tag.get ("Col")ifLen (TAG) >0{meta, OK:=M[tag]if!OK {Continue}if!value. Canset () {returnErrors. New ("struct field does not have read and write permissions")}ifLen (meta) = =0 {Continue}ifKind = =reflect. String {value. SetString (META)}Else ifKind = =reflect. Float32 {f, err:= StrConv. parsefloat (Meta, +)ifErr! =Nil {returnErr}value. SetFloat (f)}Else ifKind = =reflect. Float64 {f, err:= StrConv. parsefloat (Meta, -)ifErr! =Nil {returnErr}value. SetFloat (f)}Else ifKind = =reflect. Int64 {integer64, err:= StrConv. parseint (Meta,Ten, -)ifErr! =Nil {returnErr}value. Setint (INTEGER64)}Else ifKind = =reflect. Int {integer, err:=StrConv. Atoi (META)ifErr! =Nil {returnErr}value. Setint (Int64 (integer))}Else ifKind = =reflect. Bool {b, err:=StrConv. Parsebool (META)ifErr! =Nil {returnErr}value. Setbool (b)}Else {returnErrors. New ("unrecognized data types exist for database mappings")}}}returnNil}//Querying Datafunc (d*dao) Find (sqlstring, args ...Interface{}) *DAO {rows, err:=prokdb.query (sql, args ...)ifErr! =Nil {D.err=Errreturnd}defer rows. Close () Err=d.query (rows)ifErr! =Nil {D.err=Err}returnD}//mapping data to map[string]stringFunc (d *dao) query (rows *SQL. Rows) error {column, err:= Rows. Columns ()//read out the queried column field namesifErr! =Nil {logger. Error (ERR)returnerr}values:= Make ([]byte, Len (column))//values is the value of each column, which is obtained in ByteScans: = Make ([]Interface{}, Len (column))//because each query comes out of an indeterminate column, the length of the query is fixed with Len (column) forI: =range Values {Scans[i]= &Values[i]}results:= Make ([]map[string]string,0)//finally get the map forrows. Next () {ifERR: = rows. Scan (Scans ...); Err! =Nil {//query. The indefinite Long value of the scan query is placed in scans[i] = &values[i], i.e. each line is placed in the valueslogger. Error (ERR)returnErr}row:= Make (map[string]string)//each row of data forK, V: =Range Values {//each row of data is placed in the values, now move it to the rowKey: =Column[k]row[key]=string(v)}results=Append (results, row)}d.data=ResultsreturnNil}//pass the object address outFunc (d *dao) Unique (inch Interface{}) error {ifLen (D.data) >0 {returnD.mapping (d.data[0], reflect. ValueOf (inch))}returnNil}

Func (d *dao) List (inch Interface{}) error {ifD.err! =Nil {returnD.err} Length:=Len (d.data)ifLength >0{V:= Reflect. ValueOf (inch). Elem () NEWV:= Reflect. Makeslice (V.type (),0, Length) v.set (NEWV) v.setlen (length) Index:=0         forI: =0; i < length; i++{k:=V.type (). Elem (). Elem () NEWOBJ:=reflect. New (k) Err:=d.mapping (D.data[i], NEWOBJ)ifErr! =Nil {returnErr} v.index (Index). Set (NEWOBJ) Index++} v.setlen (index)}returnNil}

Golang notes (1)-database query results mapped to struct