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Firefox 6 introduced static functions, as part of the C++ Preferences class, for accessing preferences efficiently from within application code. This API is not available for add-ons, but if you're working on a Gecko application, this API is the preferred way to access preferences.
Due to the relatively limited target audience for this API, we don't have a thorough API reference at this time (although if you have some time, feel free to add one!). The examples below and the self-explanatory nature of most of the API should do the trick. Take a look at the source: modules/libpref/Preferences.h.
Method overview
static bool GetBool(const char* aPref, bool aDefault = false); |
static PRInt32 GetInt(const char* aPref, PRInt32 aDefault = 0); |
static PRUint32 GetUint(const char* aPref, PRUint32 aDefault = 0); |
static nsAdoptingCString GetCString(const char* aPref); |
static nsAdoptingString GetString(const char* aPref); |
static nsAdoptingCString GetLocalizedCString(const char* aPref); |
static nsAdoptingString GetLocalizedString(const char* aPref); |
static nsresult GetBool(const char* aPref, bool* aResult); |
static nsresult GetInt(const char* aPref, PRInt32* aResult); |
static nsresult GetUint(const char* aPref, PRUint32* aResult); |
static nsresult GetCString(const char* aPref, nsACString* aResult); |
static nsresult GetString(const char* aPref, nsAString* aResult); |
static nsresult GetLocalizedCString(const char* aPref, nsACString* aResult); |
static nsresult GetLocalizedString(const char* aPref, nsAString* aResult); |
static nsresult GetComplex(const char* aPref, const nsIID &aType, void** aResult); |
static nsresult SetBool(const char* aPref, bool aValue); |
static nsresult SetInt(const char* aPref, PRInt32 aValue); |
static nsresult SetUint(const char* aPref, PRUint32 aValue); |
static nsresult SetCString(const char* aPref, const char* aValue); |
static nsresult SetCString(const char* aPref, const nsACString &aValue); |
static nsresult SetString(const char* aPref, const PRUnichar* aValue); |
static nsresult SetString(const char* aPref, const nsAString &aValue); |
static nsresult SetComplex(const char* aPref, const nsIID &aType, nsISupports* aValue); |
static nsresult ClearUser(const char* aPref); |
static bool HasUserValue(const char* aPref); |
static nsresult AddStrongObserver(nsIObserver* aObserver, const char* aPref); |
static nsresult AddWeakObserver(nsIObserver* aObserver, const char* aPref); |
static nsresult RemoveObserver(nsIObserver* aObserver, const char* aPref); |
static nsresult AddStrongObservers(nsIObserver* aObserver, const char** aPrefs); |
static nsresult AddWeakObservers(nsIObserver* aObserver, const char** aPrefs); |
static nsresult RemoveObservers(nsIObserver* aObserver, const char** aPrefs); |
static nsresult RegisterCallback(PrefChangedFunc aCallback, const char* aPref, void* aClosure = nsnull); |
static nsresult UnregisterCallback(PrefChangedFunc aCallback, const char* aPref, void* aClosure = nsnull); |
static nsresult AddBoolVarCache(bool* aVariable, const char* aPref, bool aDefault = false); |
static nsresult AddIntVarCache(PRInt32* aVariable, const char* aPref, PRInt32 aDefault = 0); |
static nsresult AddUintVarCache(PRUint32* aVariable, const char* aPref, PRUint32 aDefault = 0); |
static nsresult GetDefaultBool(const char* aPref, bool* aResult); |
static nsresult GetDefaultInt(const char* aPref, PRInt32* aResult); |
static nsresult GetDefaultUint(const char* aPref, PRUint32* aResult); |
static bool GetDefaultBool(const char* aPref, bool aFailedResult); |
static PRInt32 GetDefaultInt(const char* aPref, PRInt32 aFailedResult); |
static PRUint32 GetDefaultUint(const char* aPref, PRUint32 aFailedResult); |
static nsAdoptingString GetDefaultString(const char* aPref); |
static nsAdoptingCString GetDefaultCString(const char* aPref); |
static nsAdoptingString GetDefaultLocalizedString(const char* aPref); |
static nsAdoptingCString GetDefaultLocalizedCString(const char* aPref); |
static nsresult GetDefaultCString(const char* aPref, nsACString* aResult); |
static nsresult GetDefaultString(const char* aPref, nsAString* aResult); |
static nsresult GetDefaultLocalizedCString(const char* aPref, nsACString* aResult); |
static nsresult GetDefaultLocalizedString(const char* aPref, nsAString* aResult); |
static nsresult GetDefaultComplex(const char* aPref, const nsIID &aType, void** aResult); |
Examples
Simply retrieving the value of a Boolean preference can be done like this:
bool myPref = Preferences::GetBool("preference.name.string", PR_TRUE);
This returns the value of the preference named "preference.name.string", using the default value PR_TRUE if the preference doesn't exist.