add WithOffsetFunc to define private RandomExpireCache.offset field

client/cache/random_expired_cache.go

@@ -24,29 +24,35 @@ import (
 // RandomExpireCacheOption implement genreate random time offset expired option
 type RandomExpireCacheOption func(*RandomExpireCache)
 
+// WithOffsetFunc returns a RandomExpireCacheOption that configures the offset function
+func WithOffsetFunc(fn func() time.Duration) RandomExpireCacheOption {
+	return func(cache *RandomExpireCache) {
+		cache.offset = fn
+	}
+}
+
 // RandomExpireCache prevent cache batch invalidation
 // Cache random time offset expired
 type RandomExpireCache struct {
 	Cache
-	Offset func() time.Duration
+	offset func() time.Duration
 }
 
 // Put random time offset expired
 func (rec *RandomExpireCache) Put(ctx context.Context, key string, val interface{}, timeout time.Duration) error {
-	timeout += rec.Offset()
+	timeout += rec.offset()
 	return rec.Cache.Put(ctx, key, val, timeout)
 }
 
 // NewRandomExpireCache return random expire cache struct
 func NewRandomExpireCache(adapter Cache, opts ...RandomExpireCacheOption) Cache {
-	var rec RandomExpireCache
-	rec.Cache = adapter
+	rec := RandomExpireCache{
+		Cache:  adapter,
+		offset: defaultExpiredFunc(),
+	}
 	for _, fn := range opts {
 		fn(&rec)
 	}
-	if rec.Offset == nil {
-		rec.Offset = defaultExpiredFunc()
-	}
 	return &rec
 }
 

client/cache/random_expired_cache_test.go

@@ -16,6 +16,7 @@ package cache
 
 import (
 	"context"
+	"math/rand"
 	"strings"
 	"testing"
 	"time"
@@ -27,10 +28,9 @@ func TestRandomExpireCache(t *testing.T) {
 	bm, err := NewCache("memory", `{"interval":20}`)
 	assert.Nil(t, err)
 
-	// cache := NewRandomExpireCache(bm)
-	cache := NewRandomExpireCache(bm, func(opt *RandomExpireCache) {
-		opt.Offset = defaultExpiredFunc()
-	})
+	cache := NewRandomExpireCache(bm)
+	// should not be nil
+	assert.NotNil(t, cache.(*RandomExpireCache).offset)
 
 	timeoutDuration := 3 * time.Second
 
@@ -84,5 +84,16 @@ func TestRandomExpireCache(t *testing.T) {
 
 	assert.NotNil(t, err)
 	assert.True(t, strings.Contains(err.Error(), "key isn't exist"))
-
+}
+
+func TestWithOffsetFunc(t *testing.T) {
+	bm, err := NewCache("memory", `{"interval":20}`)
+	assert.Nil(t, err)
+
+	magic := -time.Duration(rand.Int())
+	cache := NewRandomExpireCache(bm, WithOffsetFunc(func() time.Duration {
+		return magic
+	}))
+	// offset should return the magic value
+	assert.Equal(t, magic, cache.(*RandomExpireCache).offset())
 }