README.md•2.52 kB
# reflect2
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[](http://godoc.org/github.com/modern-go/reflect2)
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[](https://codecov.io/gh/modern-go/reflect2)
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reflect api that avoids runtime reflect.Value cost
* reflect get/set interface{}, with type checking
* reflect get/set unsafe.Pointer, without type checking
* `reflect2.TypeByName` works like `Class.forName` found in java
[json-iterator](https://github.com/json-iterator/go) use this package to save runtime dispatching cost.
This package is designed for low level libraries to optimize reflection performance.
General application should still use reflect standard library.
# reflect2.TypeByName
```go
// given package is github.com/your/awesome-package
type MyStruct struct {
// ...
}
// will return the type
reflect2.TypeByName("awesome-package.MyStruct")
// however, if the type has not been used
// it will be eliminated by compiler, so we can not get it in runtime
```
# reflect2 get/set interface{}
```go
valType := reflect2.TypeOf(1)
i := 1
j := 10
valType.Set(&i, &j)
// i will be 10
```
to get set `type`, always use its pointer `*type`
# reflect2 get/set unsafe.Pointer
```go
valType := reflect2.TypeOf(1)
i := 1
j := 10
valType.UnsafeSet(unsafe.Pointer(&i), unsafe.Pointer(&j))
// i will be 10
```
to get set `type`, always use its pointer `*type`
# benchmark
Benchmark is not necessary for this package. It does nothing actually.
As it is just a thin wrapper to make go runtime public.
Both `reflect2` and `reflect` call same function
provided by `runtime` package exposed by go language.
# unsafe safety
Instead of casting `[]byte` to `sliceHeader` in your application using unsafe.
We can use reflect2 instead. This way, if `sliceHeader` changes in the future,
only reflect2 need to be upgraded.
reflect2 tries its best to keep the implementation same as reflect (by testing).