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Merge pull request #46 from saireddyavs/master

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Update README.md
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Lasse Martin Jakobsen 2023-01-31 16:24:34 +01:00 committed by GitHub
parent 5a062ef696 7e2ba16f20
commit f18fd5f884
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1 changed files with 12 additions and 11 deletions
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@ -311,7 +311,7 @@ func getReference(extension string) (string, bool) {
if !ok { if !ok {
return EmptyItem, false return EmptyItem, false
} }
return refIface.(string) return refIface.(string), true
} }
func getItemByReference(reference string) (Item, error) { func getItemByReference(reference string) (Item, error) {
@ -503,6 +503,7 @@ func getVal(num int) (string, error) {
if val == "" { if val == "" {
return NewValue() // pretend function return NewValue() // pretend function
} }
return val, err
} }
func main() { func main() {
@ -813,27 +814,27 @@ There are other scenarios in which it is common to find `nil` values that can ca
```go ```go
type App struct { type App struct {
Cache *KVCache Cache *KVCache
} }
type KVCache struct { type KVCache struct {
mtx sync.RWMutex mtx sync.RWMutex
store map[string]string store map[string]string
} }
func (cache *KVCache) Add(key, value string) { func (cache *KVCache) Add(key, value string) {
cache.mtx.Lock() cache.mtx.Lock()
defer cache.mtx.Unlock() defer cache.mtx.Unlock()
cache.store[key] = value cache.store[key] = value
} }
``` ```
This code is absolutely fine. However, the danger is that our `App` can be initialised incorrectly, without initialising the `Cache` property within. Should the following code be invoked, our application will panic: This code is absolutely fine. However, the danger is that our `App` can be initialised incorrectly, without initialising the `Cache` property within. Should the following code be invoked, our application will panic:
```go ```go
app := App{} app := App{}
app.Cache.Add("panic", "now") app.Cache.Add("panic", "now")
``` ```
The `Cache` property has never been initialised and is therefore a `nil` pointer. Thus, invoking the `Add` method like we did here will cause a panic, with the following message: The `Cache` property has never been initialised and is therefore a `nil` pointer. Thus, invoking the `Add` method like we did here will cause a panic, with the following message:
@ -844,14 +845,14 @@ Instead, we can turn the `Cache` property of our `App` structure into a private
```go ```go
type App struct { type App struct {
cache *KVCache cache *KVCache
} }
func (app *App) Cache() *KVCache { func (app *App) Cache() *KVCache {
if app.cache == nil { if app.cache == nil {
app.cache = NewKVCache() app.cache = NewKVCache()
} }
return app.cache return app.cache
} }
``` ```