Golang Value.Type方法代碼示例

/*
Perform either case-sensitive or case-insensitive field lookup.
*/
func (this *Field) Apply(context Context, first, second value.Value) (value.Value, error) {
	switch second.Type() {
	case value.STRING:
		s := second.Actual().(string)
		v, ok := first.Field(s)

		if !ok && this.caseInsensitive {
			s = strings.ToLower(s)
			fields := first.Fields()
			for f, val := range fields {
				if s == strings.ToLower(f) {
					return value.NewValue(val), nil
				}
			}
		}

		return v, nil
	case value.MISSING:
		return value.MISSING_VALUE, nil
	default:
		if first.Type() == value.MISSING {
			return value.MISSING_VALUE, nil
		} else {
			return value.NULL_VALUE, nil
		}
	}
}

/*
It returns a string based on the input expr value. Values
missing, null and strings return themselves. False, true
(boolean) and numbers return their string representation.
This is done using the Sprint method defined in fmt for Go.
All other values map to null.
*/
func (this *ToString) Apply(context Context, arg value.Value) (value.Value, error) {
	switch arg.Type() {
	case value.MISSING, value.NULL, value.STRING:
		return arg, nil
	case value.BOOLEAN:
		return value.NewValue(fmt.Sprint(arg.Actual())), nil
	case value.NUMBER:
		f := arg.Actual().(float64)
		if f == -0 {
			f = 0
		}

		s := strconv.FormatFloat(f, 'f', -1, 64)
		return value.NewValue(s), nil
	case value.BINARY:
		raw, ok := arg.Actual().([]byte)
		if !ok {
			return value.NULL_VALUE, nil
		}

		s := string(raw)
		return value.NewValue(s), nil
	default:
		return value.NULL_VALUE, nil
	}
}

/*
This method returns an object value. The input of types
missing, null and object return themselves. For all other
values, return an _EMPTY_OBJECT value.
*/
func (this *ToObject) Apply(context Context, arg value.Value) (value.Value, error) {
	switch arg.Type() {
	case value.MISSING, value.NULL, value.OBJECT:
		return arg, nil
	}

	return _EMPTY_OBJECT, nil
}

/*
Evaluates the Is Missing comparison operation for expressions.
Return true if the input argument value is a missing value,
else return false.
*/
func (this *IsMissing) Apply(context Context, arg value.Value) (value.Value, error) {
	switch arg.Type() {
	case value.MISSING:
		return value.TRUE_VALUE, nil
	default:
		return value.FALSE_VALUE, nil
	}
}

/*
Return the neagation of the input value, if the type of input is a number.
For missing return a missing value, and for all other input types return a
null.
*/
func (this *Neg) Apply(context Context, arg value.Value) (value.Value, error) {
	if arg.Type() == value.NUMBER {
		return value.NewValue(-arg.Actual().(float64)), nil
	} else if arg.Type() == value.MISSING {
		return value.MISSING_VALUE, nil
	} else {
		return value.NULL_VALUE, nil
	}
}

func (this *Base64) Apply(context Context, operand value.Value) (value.Value, error) {
	if operand.Type() == value.MISSING {
		return operand, nil
	}

	bytes, _ := operand.MarshalJSON() // Ignore errors from BINARY values
	str := base64.StdEncoding.EncodeToString(bytes)
	return value.NewValue(str), nil
}

func (this *preparedCache) get(name value.Value) *Prepared {
	if name.Type() != value.STRING || !name.Truth() {
		return nil
	}
	this.RLock()
	rv := this.prepareds[name.Actual().(string)]
	this.RUnlock()
	return rv
}

/*
This method returns true if he value is an array and contains at least one element.
This is done by checking the length of the array. If the type of input value
is missing then return a missing value, and for all other types return null.
*/
func (this *Exists) Apply(context Context, arg value.Value) (value.Value, error) {
	if arg.Type() == value.ARRAY {
		a := arg.Actual().([]interface{})
		return value.NewValue(len(a) > 0), nil
	} else if arg.Type() == value.MISSING {
		return value.MISSING_VALUE, nil
	} else {
		return value.NULL_VALUE, nil
	}
}

/*
This method returns the length of the object. If the type of
input is missing then return a missing value, and if not an
object return a null value. Convert it to a valid Go type.
Cast it to a map from string to interface and return its
length by using the len function by casting it to float64.
*/
func (this *ObjectLength) Apply(context Context, arg value.Value) (value.Value, error) {
	if arg.Type() == value.MISSING {
		return value.MISSING_VALUE, nil
	} else if arg.Type() != value.OBJECT {
		return value.NULL_VALUE, nil
	}

	oa := arg.Actual().(map[string]interface{})
	return value.NewValue(float64(len(oa))), nil
}

/*
This method returns the length of the input array using
the len method. If the input value is of type missing
return a missing value, and for all non array values
return null.
*/
func (this *ArrayLength) Apply(context Context, arg value.Value) (value.Value, error) {
	if arg.Type() == value.MISSING {
		return value.MISSING_VALUE, nil
	} else if arg.Type() != value.ARRAY {
		return value.NULL_VALUE, nil
	}

	aa := arg.Actual().([]interface{})
	return value.NewValue(float64(len(aa))), nil
}

/*
This method takes in an argument value and returns its length
as value. If the input type is missing return missing, and if
it isnt string then return null value. Use the len method to
return the length of the input string. Convert it into valid
N1QL value and return.
*/
func (this *Length) Apply(context Context, arg value.Value) (value.Value, error) {
	if arg.Type() == value.MISSING {
		return value.MISSING_VALUE, nil
	} else if arg.Type() != value.STRING {
		return value.NULL_VALUE, nil
	}

	rv := len(arg.Actual().(string))
	return value.NewValue(float64(rv)), nil
}

/*
Aggregates input data by evaluating operands.For all
values other than Number, return the input value itself.
Call setAdd to compute the intermediate aggregate value
and return it.
*/
func (this *AvgDistinct) CumulateInitial(item, cumulative value.Value, context Context) (value.Value, error) {
	item, e := this.Operand().Evaluate(item, context)
	if e != nil {
		return nil, e
	}

	if item.Type() != value.NUMBER {
		return cumulative, nil
	}

	return setAdd(item, cumulative)
}

func (this *Not) Apply(context Context, arg value.Value) (value.Value, error) {
	switch arg.Type() {
	case value.MISSING, value.NULL:
		return arg, nil
	default:
		if arg.Truth() {
			return value.FALSE_VALUE, nil
		} else {
			return value.TRUE_VALUE, nil
		}
	}
}

/*
Aggregates input data by evaluating operands. For missing
item values, return the input value itself. Call
cumulatePart to compute the intermediate aggregate value
and return it.
*/
func (this *ArrayAgg) CumulateInitial(item, cumulative value.Value, context Context) (value.Value, error) {
	item, e := this.Operand().Evaluate(item, context)
	if e != nil {
		return nil, e
	}

	if item.Type() <= value.MISSING || item.Type() == value.BINARY {
		return cumulative, nil
	}

	return this.cumulatePart(value.NewValue([]interface{}{item}), cumulative, context)
}

func (this *Sum) CumulateInitial(item, cumulative value.Value, context Context) (value.Value, error) {
	item, e := this.Operand().Evaluate(item, context)
	if e != nil {
		return nil, e
	}

	if item.Type() != value.NUMBER {
		return cumulative, nil
	}

	return this.cumulatePart(item, cumulative, context)
}