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property.go
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property.go
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// Copyright (C) 2018 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package api
import (
"reflect"
"github.com/google/gapid/core/data/deep"
"github.com/google/gapid/core/data/generic"
)
// Property represents a single field on an object.
// A Property has a getter for reading the field value, and an optional setter
// for assigning to the field.
type Property struct {
// Name of the property.
Name string
// Type of the value.
Type reflect.Type
// Get gets the property value from the given object.
Get func() interface{}
// Set assigns the value to the property on the given object.
// For read-only properties Set may be nil.
Set func(value interface{})
// Constants is the optional index of the constant set used by the value.
// -1 represents no constant set.
Constants int
}
// SetConstants is a helper method for setting the Constants field in a
// fluent expression.
func (p *Property) SetConstants(idx int) *Property {
p.Constants = idx
return p
}
// Properties is a list of property pointers.
type Properties []*Property
// PropertyProvider is the interface implemented by types that provide
// properties.
type PropertyProvider interface {
Properties() Properties
}
// NewProperty returns a new Property using the given getter and setter
// functions. set may be nil in the case of a read-only property.
func NewProperty(name string, get, set interface{}) *Property {
type Value = generic.T1
var ValueTy = generic.T1Ty
sigs := []generic.Sig{generic.Sig{Name: "get", Interface: func() Value { return Value{} }, Function: get}}
if set != nil {
sigs = append(sigs, generic.Sig{Name: "set", Interface: func(Value) {}, Function: set})
}
m := generic.CheckSigs(sigs...)
if !m.Ok() {
panic(m.Errors)
}
g, s := reflect.ValueOf(get), reflect.ValueOf(set)
ty := m.Bindings[ValueTy]
out := &Property{
Name: name,
Type: ty,
Get: func() interface{} { return g.Call([]reflect.Value{})[0].Interface() },
Constants: -1,
}
if set != nil {
out.Set = func(value interface{}) {
v := reflect.ValueOf(value)
if ty == v.Type() {
// No cast needed.
s.Call([]reflect.Value{v})
return
}
c := reflect.New(ty)
if err := deep.Copy(c.Interface(), v.Interface()); err != nil {
panic(err)
}
s.Call([]reflect.Value{c.Elem()})
}
}
return out
}
// Find returns the property with the given name, or nil if no matching
// property is found.
func (l Properties) Find(name string) *Property {
for _, p := range l {
if p.Name == name {
return p
}
}
return nil
}