README.md
1# reflect2
2
3[](https://sourcegraph.com/github.com/modern-go/reflect2?badge)
4[](http://godoc.org/github.com/modern-go/reflect2)
5[](https://travis-ci.org/modern-go/reflect2)
6[](https://codecov.io/gh/modern-go/reflect2)
7[](https://goreportcard.com/report/github.com/modern-go/reflect2)
8[](https://raw.githubusercontent.com/modern-go/reflect2/master/LICENSE)
9
10reflect api that avoids runtime reflect.Value cost
11
12* reflect get/set interface{}, with type checking
13* reflect get/set unsafe.Pointer, without type checking
14* `reflect2.TypeByName` works like `Class.forName` found in java
15
16[json-iterator](https://github.com/json-iterator/go) use this package to save runtime dispatching cost.
17This package is designed for low level libraries to optimize reflection performance.
18General application should still use reflect standard library.
19
20# reflect2.TypeByName
21
22```go
23// given package is github.com/your/awesome-package
24type MyStruct struct {
25 // ...
26}
27
28// will return the type
29reflect2.TypeByName("awesome-package.MyStruct")
30// however, if the type has not been used
31// it will be eliminated by compiler, so we can not get it in runtime
32```
33
34# reflect2 get/set interface{}
35
36```go
37valType := reflect2.TypeOf(1)
38i := 1
39j := 10
40valType.Set(&i, &j)
41// i will be 10
42```
43
44to get set `type`, always use its pointer `*type`
45
46# reflect2 get/set unsafe.Pointer
47
48```go
49valType := reflect2.TypeOf(1)
50i := 1
51j := 10
52valType.UnsafeSet(unsafe.Pointer(&i), unsafe.Pointer(&j))
53// i will be 10
54```
55
56to get set `type`, always use its pointer `*type`
57
58# benchmark
59
60Benchmark is not necessary for this package. It does nothing actually.
61As it is just a thin wrapper to make go runtime public.
62Both `reflect2` and `reflect` call same function
63provided by `runtime` package exposed by go language.
64
65# unsafe safety
66
67Instead of casting `[]byte` to `sliceHeader` in your application using unsafe.
68We can use reflect2 instead. This way, if `sliceHeader` changes in the future,
69only reflect2 need to be upgraded.
70
71reflect2 tries its best to keep the implementation same as reflect (by testing).
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