【golang】【源代码】reflect.DeepEqual(x,y)函数

reflect.DeepEqual(x, y)函数

功能是比较x和y是否一致，x和y不仅限于基础类型，也可以是像array、 slice、 map、 ptr、struct、interface类型，在代码中经常能见到。
一起看下是怎么实现的吧~

func DeepEqual(x, y interface{}) bool {if x == nil || y == nil {return x == y}v1 := ValueOf(x)v2 := ValueOf(y)if v1.Type() != v2.Type() {return false}return deepValueEqual(v1, v2, make(map[visit]bool), 0)
}

1. 先判断x和y是否为空，一方为空，另一方不为空则肯定不相等；两者都为空那就相等。
2. 判断类型是否一致，如果x和y类型都不一致，那肯定不相等。

继续比较，

func deepValueEqual(v1, v2 Value, visited map[visit]bool, depth int) bool {if !v1.IsValid() || !v2.IsValid() {return v1.IsValid() == v2.IsValid()}if v1.Type() != v2.Type() {return false}// if depth > 10 { panic("deepValueEqual") }	// for debugging// We want to avoid putting more in the visited map than we need to.// For any possible reference cycle that might be encountered,// hard(t) needs to return true for at least one of the types in the cycle.hard := func(k Kind) bool {switch k {case Map, Slice, Ptr, Interface:return true}return false}if v1.CanAddr() && v2.CanAddr() && hard(v1.Kind()) {addr1 := unsafe.Pointer(v1.UnsafeAddr())addr2 := unsafe.Pointer(v2.UnsafeAddr())if uintptr(addr1) > uintptr(addr2) {// Canonicalize order to reduce number of entries in visited.// Assumes non-moving garbage collector.addr1, addr2 = addr2, addr1}// Short circuit if references are already seen.typ := v1.Type()v := visit{addr1, addr2, typ}if visited[v] {return true}// Remember for later.visited[v] = true}switch v1.Kind() {case Array:for i := 0; i < v1.Len(); i++ {if !deepValueEqual(v1.Index(i), v2.Index(i), visited, depth+1) {return false}}return truecase Slice:if v1.IsNil() != v2.IsNil() {return false}if v1.Len() != v2.Len() {return false}if v1.Pointer() == v2.Pointer() {return true}for i := 0; i < v1.Len(); i++ {if !deepValueEqual(v1.Index(i), v2.Index(i), visited, depth+1) {return false}}return truecase Interface:if v1.IsNil() || v2.IsNil() {return v1.IsNil() == v2.IsNil()}return deepValueEqual(v1.Elem(), v2.Elem(), visited, depth+1)case Ptr:if v1.Pointer() == v2.Pointer() {return true}return deepValueEqual(v1.Elem(), v2.Elem(), visited, depth+1)case Struct:for i, n := 0, v1.NumField(); i < n; i++ {if !deepValueEqual(v1.Field(i), v2.Field(i), visited, depth+1) {return false}}return truecase Map:if v1.IsNil() != v2.IsNil() {return false}if v1.Len() != v2.Len() {return false}if v1.Pointer() == v2.Pointer() {return true}for _, k := range v1.MapKeys() {val1 := v1.MapIndex(k)val2 := v2.MapIndex(k)if !val1.IsValid() || !val2.IsValid() || !deepValueEqual(val1, val2, visited, depth+1) {return false}}return truecase Func:if v1.IsNil() && v2.IsNil() {return true}// Can't do better than this:return falsedefault:// Normal equality sufficesreturn valueInterface(v1, false) == valueInterface(v2, false)}
}

1. 如果是slice map ptr interface 类型，hard 返回true; 如果是array 原始元素类型hard返回false。
2. 拿slice类型举个例子，会先判断x和y是否为空，会判断x和y的长度是否一致，判断是否指向同一指针，然后递归比较各个元素。
3. 注意&Person{name1,age1} 是ptr类型，Person{name1,age1}是struct类型。
4. 注意如果是func类型，如果两个func都会nil时认为x和y一致，否则被判定为不一致。

大家可以用各种例子试一试，debug一下