Add `ToInt8`, `ToInt16` and `ToInt32`

cast.go

@@ -32,6 +32,21 @@ func ToInt64(i interface{}) int64 {
 	return v
 }
 
+func ToInt32(i interface{}) int32 {
+	v, _ := ToInt32E(i)
+	return v
+}
+
+func ToInt16(i interface{}) int16 {
+	v, _ := ToInt16E(i)
+	return v
+}
+
+func ToInt8(i interface{}) int8 {
+	v, _ := ToInt8E(i)
+	return v
+}
+
 func ToInt(i interface{}) int {
 	v, _ := ToIntE(i)
 	return v

cast_test.go

@@ -34,6 +34,39 @@ func TestToInt64(t *testing.T) {
 	assert.Equal(t, ToInt64(eight), int64(8))
 }
 
+func TestToInt32(t *testing.T) {
+	var eight interface{} = 8
+	assert.Equal(t, ToInt32(int32(8)), int32(8))
+	assert.Equal(t, ToInt32(8), int32(8))
+	assert.Equal(t, ToInt32(8.31), int32(8))
+	assert.Equal(t, ToInt32("8"), int32(8))
+	assert.Equal(t, ToInt32(true), int32(1))
+	assert.Equal(t, ToInt32(false), int32(0))
+	assert.Equal(t, ToInt32(eight), int32(8))
+}
+
+func TestToInt16(t *testing.T) {
+	var eight interface{} = 8
+	assert.Equal(t, ToInt16(int16(8)), int16(8))
+	assert.Equal(t, ToInt16(8), int16(8))
+	assert.Equal(t, ToInt16(8.31), int16(8))
+	assert.Equal(t, ToInt16("8"), int16(8))
+	assert.Equal(t, ToInt16(true), int16(1))
+	assert.Equal(t, ToInt16(false), int16(0))
+	assert.Equal(t, ToInt16(eight), int16(8))
+}
+
+func TestToInt8(t *testing.T) {
+	var eight interface{} = 8
+	assert.Equal(t, ToInt8(int8(8)), int8(8))
+	assert.Equal(t, ToInt8(8), int8(8))
+	assert.Equal(t, ToInt8(8.31), int8(8))
+	assert.Equal(t, ToInt8("8"), int8(8))
+	assert.Equal(t, ToInt8(true), int8(1))
+	assert.Equal(t, ToInt8(false), int8(0))
+	assert.Equal(t, ToInt8(eight), int8(8))
+}
+
 func TestToFloat64(t *testing.T) {
 	var eight interface{} = 8
 	assert.Equal(t, ToFloat64(8), 8.00)

caste.go

@@ -151,6 +151,111 @@ func ToInt64E(i interface{}) (int64, error) {
 	}
 }
 
+// ToInt32E casts an empty interface to an int32.
+func ToInt32E(i interface{}) (int32, error) {
+	i = indirect(i)
+
+	switch s := i.(type) {
+	case int64:
+		return int32(s), nil
+	case int:
+		return int32(s), nil
+	case int32:
+		return s, nil
+	case int16:
+		return int32(s), nil
+	case int8:
+		return int32(s), nil
+	case string:
+		v, err := strconv.ParseInt(s, 0, 0)
+		if err == nil {
+			return int32(v), nil
+		}
+		return 0, fmt.Errorf("Unable to Cast %#v to int32", i)
+	case float64:
+		return int32(s), nil
+	case bool:
+		if bool(s) {
+			return int32(1), nil
+		}
+		return int32(0), nil
+	case nil:
+		return int32(0), nil
+	default:
+		return int32(0), fmt.Errorf("Unable to Cast %#v to int32", i)
+	}
+}
+
+// ToInt16E casts an empty interface to an int16.
+func ToInt16E(i interface{}) (int16, error) {
+	i = indirect(i)
+
+	switch s := i.(type) {
+	case int64:
+		return int16(s), nil
+	case int:
+		return int16(s), nil
+	case int32:
+		return int16(s), nil
+	case int16:
+		return s, nil
+	case int8:
+		return int16(s), nil
+	case string:
+		v, err := strconv.ParseInt(s, 0, 0)
+		if err == nil {
+			return int16(v), nil
+		}
+		return 0, fmt.Errorf("Unable to Cast %#v to int16", i)
+	case float64:
+		return int16(s), nil
+	case bool:
+		if bool(s) {
+			return int16(1), nil
+		}
+		return int16(0), nil
+	case nil:
+		return int16(0), nil
+	default:
+		return int16(0), fmt.Errorf("Unable to Cast %#v to int16", i)
+	}
+}
+
+// ToInt8E casts an empty interface to an int8.
+func ToInt8E(i interface{}) (int8, error) {
+	i = indirect(i)
+
+	switch s := i.(type) {
+	case int64:
+		return int8(s), nil
+	case int:
+		return int8(s), nil
+	case int32:
+		return int8(s), nil
+	case int16:
+		return int8(s), nil
+	case int8:
+		return s, nil
+	case string:
+		v, err := strconv.ParseInt(s, 0, 0)
+		if err == nil {
+			return int8(v), nil
+		}
+		return 0, fmt.Errorf("Unable to Cast %#v to int8", i)
+	case float64:
+		return int8(s), nil
+	case bool:
+		if bool(s) {
+			return int8(1), nil
+		}
+		return int8(0), nil
+	case nil:
+		return int8(0), nil
+	default:
+		return int8(0), fmt.Errorf("Unable to Cast %#v to int8", i)
+	}
+}
+
 // ToIntE casts an empty interface to an int.
 func ToIntE(i interface{}) (int, error) {
 	i = indirect(i)