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    nsIPrefBranch

    このインターフェースは preferences dataを操作するために使われます。対応するオブジェクトはpreferences service (nsIPrefService) から取得することができ、デフォルト値やアプリケーションのuser preferencesを参照したり変更したりするために使うことができます。
    継承元: nsISupports 最終更新: Gecko 13 (Firefox 13 / Thunderbird 13 / SeaMonkey 2.10)

    このオブジェクトは自身が指し示す"branch"の起点となるpreference木の"root"値を伴って生成されます。各preferencesにはこのrootに続く最後の部分のみを使ってアクセスすることができます。 例えばオブジェクトが"browser.startup."をrootとして生成された場合、"browser.startup.page"、"browser.startup.homepage"、"browser.startup.homepage_override"などに対してGet/Setを行う際には"page"、"homepage"、"homepage_override"と指定することができます。

    Method overview

    void addObserver(in string aDomain, in nsIObserver aObserver, in boolean aHoldWeak);
    void clearUserPref(in string aPrefName);
    void deleteBranch(in string aStartingAt);
    boolean getBoolPref(in string aPrefName);
    string getCharPref(in string aPrefName);
    void getChildList(in string aStartingAt, [optional] out unsigned long aCount, [array, size_is(aCount), retval] out string aChildArray);
    void getComplexValue(in string aPrefName, in nsIIDRef aType, [iid_is(aType), retval] out nsQIResult aValue);
    long getIntPref(in string aPrefName);
    long getPrefType(in string aPrefName);
    void lockPref(in string aPrefName);
    boolean prefHasUserValue(in string aPrefName);
    boolean prefIsLocked(in string aPrefName);
    void removeObserver(in string aDomain, in nsIObserver aObserver);
    void resetBranch(in string aStartingAt);
    void setBoolPref(in string aPrefName, in long aValue);
    void setCharPref(in string aPrefName, in string aValue);
    void setComplexValue(in string aPrefName, in nsIIDRef aType, in nsISupports aValue);
    void setIntPref(in string aPrefName, in long aValue);
    void unlockPref(in string aPrefName);

    Attributes

    Attribute Type Description
    root string Called to get the root on which this branch is based, such as "browser.startup." Read only.

    Constants

    Constant Value Description
    PREF_INVALID 0 long
    PREF_STRING 32 long data type.
    PREF_INT 64 long data type.
    PREF_BOOL 128 long data type.

    Methods

    要 Gecko 13 (Firefox 13 / Thunderbird 13 / SeaMonkey 2.10)

    addObserver()

    preference change observerを追加します。preferenceに変化があると以下の引数がnsIObserver.observe()に渡されます:

    aSubject - nsIPrefBranch オブジェクト (this)。

    aTopicNS_PREFBRANCH_PREFCHANGE_TOPIC_ID で定義される文字列。

    aData - 変更があったpreferenceの名前(aSubjectの"root"に対する相対値)

    aSubject.get*Pref(aData) で変更後の新しい値を得ることができます。例えば observer がaddObserver("bar.", ...)で"foo."を起点とするbranchに対して登録を行った場合、"foo.bar.baz"に対する変更がそのobserverを起こします。その時のaDataは"bar.baz"になります。

    void addObserver(
      in string aDomain, 
      in nsIObserver aObserver, 
      in boolean aHoldWeak
    );
    
    Parameters
    aDomain
    変更を監視したい preference 。完全なbranchを指定することもできます。 例えば "root" prefbranch から addObserver("foo.bar.", ...) を呼ぶと foo.bar.baz と foo.bar.bzipを監視できます
    aObserver
    preference の変更通知を受け取るオブジェクト。
    aHoldWeak
    true を指定すると aObserver の weak reference を保持します。この場合オブジェクトは nsISupportsWeakReference インターフェースを実装する必要があり、実装されていない場合は失敗します。false を指定すると strong reference を保持します。

    clearUserPref()

    Called to clear a user set value from a specific preference. This will, in effect, reset the value to the default value. If no default value exists the preference will cease to exist.

    註: This method does nothing if the prefbranch it is called on is a default branch.

    void clearUserPref(
      in string aPrefName
    );
    
    Parameters
    aPrefName
    The preference to be cleared.
    Remarks

    Gecko 6.0 note
    (Firefox 6.0 / Thunderbird 6.0 / SeaMonkey 2.3)

    Prior to Gecko 6.0 (Firefox 6.0 / Thunderbird 6.0 / SeaMonkey 2.3), this method would throw an exception if there was no user value set for the specified preference. Now, this method never throws. Instead, it simply does nothing.

    deleteBranch()

    Called to remove all of the preferences referenced by this branch.

    註: This method can be called on either a default or user branch but, in effect, always operates on both.

    void deleteBranch(
      in string aStartingAt
    );
    
    Parameters
    aStartingAt
    The point on the branch at which to start the deleting preferences. Pass in "" to remove all preferences referenced by this branch.

    getBoolPref()

    Called to get the state of an individual boolean preference.

    boolean getBoolPref(
      in string aPrefName
    );
    
    Parameters
    aPrefName
    The boolean preference to get the state of.
    Return value

    The value of the requested boolean preference.

    getCharPref()

    Called to get the state of an individual string preference.

    string getCharPref(
      in string aPrefName
    );
    
    Parameters
    aPrefName
    The string preference to retrieve.
    Return value

    Returns string - The value of the requested string preference.

    getChildList()

    Returns an array of strings representing the child preferences of the root of this branch.

    註: This method can be called on either a default or user branch but, in effect, always operates on both.

    (To call from javascript use children = nsIPrefBranch.getChildList("",obj), which will fill in obj.value with the count and return an array of keys! (It is not void in javascript)

    void getChildList(
      in string aStartingAt,
      out unsigned long aCount,
      [array, size_is(aCount), retval] out string aChildArray
    );
    
    Parameters
    aStartingAt
    The point on the branch at which to start enumerating the child preferences. Pass in "" to enumerate all preferences referenced by this branch.
    aCount Optional from Gecko 2.0
    Receives the number of elements in the array.
    aChildArray
    Receives the array of child preferences.

    getComplexValue()

    Called to get the state of an individual complex preference. A complex preference is a preference which represents an XPCOM object that can not be easily represented using a standard boolean, integer or string value.

    void getComplexValue(
      in string aPrefName,
      in nsIIDRef aType,
      [iid_is(aType), retval] out nsQIResult aValue
    );
    
    Parameters
    aPrefName
    The complex preference to get the value of.
    aType
    The XPCOM interface that this complex preference represents. Interfaces currently supported are:
    aValue
    The XPCOM object into which to the complex preference value should be retrieved.

    getIntPref()

    Called to get the state of an individual integer preference.

    long getIntPref(
      in string aPrefName
    );
    
    Parameters
    aPrefName
    The integer preference to get the value of.
    Return value

    Returns long - The value of the requested integer preference.

    getPrefType()

    Called to determine the type of a specific preference.

    long getPrefType(
      in string aPrefName
    );
    
    Parameters
    aPrefName
    The preference to get the type of.
    Return value

    Returns long - A value representing the type of the preference. This value will be PREF_STRING, PREF_INT, PREF_BOOL, or PREF_INVALID.

    lockPref()

    Called to lock a specific preference. Locking a preference will cause the preference service to always return the default value regardless of whether there is a user set value or not.

    註: This method can be called on either a default or user branch but, in effect, always operates on the default branch.

    void lockPref(
      in string aPrefName
    );
    
    Parameters
    aPrefName
    The preference to be locked.

    prefHasUserValue()

    Called to check if a specific preference has a user value associated to it.

    註: This method can be called on either a default or user branch but, in effect, always operates on the user branch.

    註: If a preference was manually set to a value that equals the default value, then the preference no longer has a user set value, i.e. it is considered reset to its default value. In particular, this method will return false for such a preference and the preference will not be saved to a file by nsIPrefService.savePrefFile().

    boolean prefHasUserValue(
      in string aPrefName
    );
    
    Parameters
    aPrefName
    The preference to be tested.
    Return value

    Returns boolean - true The preference has a user set value. false The preference only has a default value.

    prefIsLocked()

    Called to check if a specific preference is locked. If a preference is locked calling its Get method will always return the default value.

    註: This method can be called on either a default or user branch but, in effect, always operates on the default branch.

    boolean prefIsLocked(
      in string aPrefName
    );
    
    Parameters
    aPrefName
    The preference to be tested.
    Return value

    Returns boolean - true The preference is locked. false The preference is not locked.

    要 Gecko 13 (Firefox 13 / Thunderbird 13 / SeaMonkey 2.10)

    removeObserver()

    Remove a preference change observer.

    註: You must call removeObserver method on the same nsIPrefBranch instance on which you called addObserver method in order to remove aObserver; otherwise, the observer will not be removed.

      void removeObserver(
         in string aDomain, 
         in nsIObserver aObserver
      );
    
    Parameters
    aDomain
    The preference which is being observed for changes.
    aObserver
    An observer previously registered with addObserver.

    resetBranch()

    Called to reset all of the preferences referenced by this branch to their default values.

    註: This method can be called on either a default or user branch but, in effect, always operates on the user branch.

    註: As of Firefox 3.0, this function has not yet been implemented.

    void resetBranch(
      in string aStartingAt
    );
    
    Parameters
    aStartingAt
    The point on the branch at which to start the resetting preferences to their default values. Pass in "" to reset all preferences referenced by this branch.

    setBoolPref()

    Called to set the state of an individual boolean preference.

    void setBoolPref(
      in string aPrefName,
      in long aValue
    );
    
    Parameters
    aPrefName
    The boolean preference to set the state of.
    aValue
    The boolean value to set the preference to.

    setCharPref()

    Called to set the state of an individual string preference.

    Note: preferences システムは大量のデータを保持するようには設計されていません。全ての preferences は単一のファイルに保存されアプリケーションが立ち上がる際に読み込まれます。文字列のpreferenceが最大どれだけのデータが保存できるだろうかと疑問に思った場合は、flat file や sqlite database など別の方法で保存することを検討してください。
    void setCharPref(
      in string aPrefName,
      in string aValue
    );
    
    Parameters
    aPrefName
    The string preference to set.
    aValue
    The string value to set the preference to.

    setComplexValue()

    Called to set the state of an individual complex preference. A complex preference is a preference which represents an XPCOM object that can not be easily represented using a standard boolean, integer or string value.

    void setComplexValue(
      in string aPrefName,
      in nsIIDRef aType,
      in nsISupports aValue
    );
    
    Parameters
    aPrefName
    The complex preference to set the value of.
    aType
    The XPCOM interface that this complex preference represents. Interfaces currently supported are:
    aValue
    The XPCOM object from which to set the complex preference value.

    setIntPref()

    Called to set the state of an individual integer preference.

    void setIntPref(
      in string aPrefName,
      in long aValue
    );
    
    Parameters
    aPrefName
    The integer preference to set the value of.
    aValue
    The integer value to set the preference to.

    unlockPref()

    Called to unlock a specific preference. Unlocking a previously locked preference allows the preference service to once again return the user set value of the preference.

    註: This method can be called on either a default or user branch but, in effect, always operates on the default branch.

    void unlockPref(
      in string aPrefName
    );
    
    Parameters
    aPrefName
    The preference to be unlocked.

    Remarks

    Registering as a preference observer can open an object to potential cyclical references which will cause memory leaks. These cycles generally occur because an object both registers itself as an observer (causing the branch to hold a reference to the observer) and holds a reference to the branch object for the purpose of getting/setting preference values. There are 3 approaches which have been implemented in an attempt to avoid these situations:

    1. The nsPrefBranch object supports nsISupportsWeakReference. Any consumer may hold a weak reference to it instead of a strong one.
    2. The nsPrefBranch object listens for xpcom-shutdown and frees all of the objects currently in its observer list. This ensures that long lived objects (services for example) will be freed correctly.
    3. The observer can request to be held as a weak reference when it is registered. This insures that shorter lived objects (say one tied to an open window) will not fall into the cyclical reference trap.

    The list of registered observers may be changed during the dispatch of nsPref:changed notification. However, the observers are not guaranteed to be notified in any particular order, so you can't be sure whether the added/removed observer will be called during the notification when it is added/removed. 

    It is possible to change preferences during the notification.

    It is not safe to change observers during this callback in releases before Gecko 1.9. If you want a safe way to remove a preference observer, please use an nsITimer.

    ドキュメントのタグと貢献者

    Contributors to this page: sou3ilow
    最終更新者: sou3ilow,