go-pkg/expr
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data-cursor.go: the inizialization of the current item is done in the Next() method.

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This allows the application of the filter and map operator to the first item too.
This commit is contained in:
Celestino Amoroso 2024-07-23 05:46:37 +02:00
parent dfae593e86
commit 315f5b22d3
1 changed files with 32 additions and 19 deletions
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51
data-cursor.go
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@ -5,13 +5,13 @@
package expr package expr
import ( import (
"errors"
"io" "io"
) )
type dataCursor struct { type dataCursor struct {
ds map[string]Functor ds map[string]Functor
ctx ExprContext ctx ExprContext
initState bool // true if no item has prodiced yet (this replace di initial Next() call in the contructor)
index int index int
count int count int
current any current any
@ -24,18 +24,19 @@ type dataCursor struct {
func NewDataCursor(ctx ExprContext, ds map[string]Functor, resource any) (dc *dataCursor) { func NewDataCursor(ctx ExprContext, ds map[string]Functor, resource any) (dc *dataCursor) {
dc = &dataCursor{ dc = &dataCursor{
ds: ds, ds: ds,
index: -1, initState: true,
count: 0, index: -1,
current: nil, count: 0,
lastErr: nil, current: nil,
resource: resource, lastErr: nil,
ctx: ctx.Clone(), resource: resource,
nextFunc: ds[NextName], ctx: ctx.Clone(),
nextFunc: ds[NextName],
cleanFunc: ds[CleanName], cleanFunc: ds[CleanName],
resetFunc: ds[ResetName], resetFunc: ds[ResetName],
} }
dc.Next() //dc.Next()
return return
} }
@ -107,12 +108,14 @@ func (dc *dataCursor) Reset() (success bool, err error) {
if dc.resetFunc != nil { if dc.resetFunc != nil {
if dc.resource != nil { if dc.resource != nil {
ctx := cloneContext(dc.ctx) ctx := cloneContext(dc.ctx)
if _, err = dc.resetFunc.Invoke(ctx, ResetName, []any{dc.resource}); err == nil { _, err = dc.resetFunc.Invoke(ctx, ResetName, []any{dc.resource})
dc.index = -1
dc.count = 0
}
exportObjects(dc.ctx, ctx) exportObjects(dc.ctx, ctx)
dc.Next() dc.index = -1
dc.count = 0
dc.initState = true
dc.current = nil
dc.lastErr = nil
//dc.Next()
} else { } else {
err = errInvalidDataSource() err = errInvalidDataSource()
} }
@ -128,19 +131,21 @@ func (dc *dataCursor) Clean() (success bool, err error) {
if dc.resource != nil { if dc.resource != nil {
ctx := cloneContext(dc.ctx) ctx := cloneContext(dc.ctx)
_, err = dc.cleanFunc.Invoke(ctx, CleanName, []any{dc.resource}) _, err = dc.cleanFunc.Invoke(ctx, CleanName, []any{dc.resource})
dc.resource = nil // dc.resource = nil
exportObjects(dc.ctx, ctx) exportObjects(dc.ctx, ctx)
} else { } else {
err = errInvalidDataSource() err = errInvalidDataSource()
} }
} else { } else {
err = errors.New("no 'clean' function defined in the data-source") err = errNoOperation(CleanName)
} }
success = err == nil success = err == nil
return return
} }
func (dc *dataCursor) Current() (item any, err error) { // must return io.EOF at the last item func (dc *dataCursor) Current() (item any, err error) { // must return io.EOF at the last item
dc.init()
if dc.current != nil { if dc.current != nil {
item = dc.current item = dc.current
} else { } else {
@ -167,8 +172,17 @@ func (dc *dataCursor) mapItem(mapper Functor, item any) (mappedItem any, err err
return return
} }
func (dc *dataCursor) init() {
if dc.initState {
dc.initState = false
dc.Next()
}
}
func (dc *dataCursor) Next() (current any, err error) { // must return io.EOF after the last item func (dc *dataCursor) Next() (current any, err error) { // must return io.EOF after the last item
if err = dc.lastErr; err != nil { if dc.initState {
dc.init()
} else if err = dc.lastErr; err != nil {
return return
} }
current = dc.current current = dc.current
@ -214,7 +228,6 @@ func (dc *dataCursor) Index() int {
return dc.index - 1 return dc.index - 1
} }
func (dc *dataCursor) Count() int { func (dc *dataCursor) Count() int {
return dc.count return dc.count
} }