structure: Add Has() method, fix IsZero()

README.md

@@ -45,8 +45,12 @@ f := structure.Fields(s)
 // => "Server"
 n := structure.Name(s)
 
+// Check if field name exists
+// => true
+n := structure.Has(s, "Enabled")
+
 // Check if the fields of a struct is initialized or not.
-if structure.IsZero(s) {
+if !structure.IsZero(s) {
     fmt.Println("s is initialized")
 }
 

structure.go

@@ -80,7 +80,7 @@ func Values(s interface{}) []interface{} {
 
 }
 
-// IsZero returns true if all fields in a struct are initialized (non zero
+// IsZero returns true if any field in a struct is not initialized (zero
 // value). A struct tag with the content of "-" ignores the checking of that
 // particular field. Example:
 //
@@ -96,8 +96,8 @@ func IsZero(s interface{}) bool {
 		val := v.Field(i)
 		if IsStruct(val.Interface()) {
 			ok := IsZero(val.Interface())
-			if !ok {
-				return false
+			if ok {
+				return true
 			}
 
 			continue
@@ -110,11 +110,11 @@ func IsZero(s interface{}) bool {
 		current := v.Field(i).Interface()
 
 		if reflect.DeepEqual(current, zero) {
-			return false
+			return true
 		}
 	}
 
-	return true
+	return false
 }
 
 // Fields returns a slice of field names. A struct tag with the content of "-"
@@ -172,6 +172,28 @@ func Name(s interface{}) string {
 	return t.Name()
 }
 
+// Has returns true if the given field name exists for the struct s. It panic's
+// if s's kind is not struct.
+func Has(s interface{}, fieldName string) bool {
+	v, fields := strctInfo(s)
+
+	for i, field := range fields {
+		val := v.Field(i)
+
+		if IsStruct(val.Interface()) {
+			if ok := Has(val.Interface(), fieldName); ok {
+				return true
+			}
+		}
+
+		if field.Name == fieldName {
+			return true
+		}
+	}
+
+	return false
+}
+
 // strctInfo returns the struct value and the exported struct fields for a
 // given s struct. This is a convenient helper method to avoid duplicate code
 // in some of the functions.

structure_example_test.go

@@ -110,7 +110,7 @@ func ExampleIsZero() {
 	a := &Access{
 		LastAccessed: time.Now(),
 	}
-	validA := IsZero(a)
+	isZeroA := IsZero(a)
 
 	// Name and Number is initialized.
 	b := &Access{
@@ -118,11 +118,31 @@ func ExampleIsZero() {
 		LastAccessed: time.Now(),
 		Number:       12345,
 	}
-	validB := IsZero(b)
+	isZeroB := IsZero(b)
 
-	fmt.Printf("%#v\n", validA)
-	fmt.Printf("%#v\n", validB)
+	fmt.Printf("%#v\n", isZeroA)
+	fmt.Printf("%#v\n", isZeroB)
 	// Output:
-	// false
 	// true
+	// false
+}
+
+func ExampleHas() {
+	type Access struct {
+		Name         string
+		LastAccessed time.Time
+		Number       int
+	}
+
+	s := &Access{
+		Name:         "Fatih",
+		LastAccessed: time.Now(),
+		Number:       1234567,
+	}
+
+	found := Has(s, "LastAccessed")
+
+	fmt.Printf("Has: %+v\n", found)
+	// Output:
+	// Has: true
 }

structure_test.go

@@ -357,8 +357,8 @@ func TestIsZero(t *testing.T) {
 	}
 
 	ok := IsZero(T)
-	if ok {
-		t.Error("IsZero should return false because D is not initialized")
+	if !ok {
+		t.Error("IsZero should return true because A and B are initialized.")
 	}
 
 	var X = struct {
@@ -369,8 +369,21 @@ func TestIsZero(t *testing.T) {
 	}
 
 	ok = IsZero(X)
+	if !ok {
+		t.Error("IsZero should return true because A is initialized")
+	}
+
+	var Y = struct {
+		A string
+		B int
+	}{
+		A: "a-value",
+		B: 123,
+	}
+
+	ok = IsZero(Y)
 	if ok {
-		t.Error("IsZero should return false because F is not initialized")
+		t.Error("IsZero should return false because A and B is initialized")
 	}
 }
 
@@ -388,8 +401,8 @@ func TestIsZero_Nested(t *testing.T) {
 	b := &B{A: a, C: 123}
 
 	ok := IsZero(b)
-	if ok {
-		t.Error("IsZero should return false because D is not initialized")
+	if !ok {
+		t.Error("IsZero should return true because D is not initialized")
 	}
 }
 
@@ -408,11 +421,38 @@ func TestIsZero_Anonymous(t *testing.T) {
 	b.A = a
 
 	ok := IsZero(b)
-	if ok {
+	if !ok {
 		t.Error("IsZero should return false because D is not initialized")
 	}
 }
 
+func TestHas(t *testing.T) {
+	type A struct {
+		Name string
+		D    string
+	}
+	a := A{Name: "example"}
+
+	type B struct {
+		A
+		C int
+	}
+	b := &B{C: 123}
+	b.A = a
+
+	if !Has(b, "Name") {
+		t.Error("Has should return true for Name, but it's false")
+	}
+
+	if Has(b, "NotAvailable") {
+		t.Error("Has should return false for NotAvailable, but it's true")
+	}
+
+	if !Has(b, "C") {
+		t.Error("Has should return true for C, but it's false")
+	}
+}
+
 func TestName(t *testing.T) {
 	type Foo struct {
 		A string