UINavigation backItem

Bonjour à  tous,



voila mon problème, j'ai une viewController contenant une grille, permettant d'afficher des fichier et des répertoires, mais j'ai aussi la possibilité de me promener dans l'arborescence de mes répertoires, en push. Du coup j'ai une UINavigationController et je constate que au fur et à  mesure que je change de vue, j'ai le backItem qui s'affiche à  gauche et je souhaiterais pourvoir le masquer, voir le supprimer mais j'y arrive pas. Pourtant j'ai essayé la méthode suivante mais je m'en sors pas.

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[color=#401082][color=#000000]	[[[/color][color=#b41ca4]self[/color][color=#000000] [/color]navigationController[color=#000000]] [/color]setNavigationBarHidden[color=#000000]:[/color][color=#b41ca4]NO[/color][color=#000000] [/color]animated[color=#000000]:[/color][color=#b41ca4]NO[/color][color=#000000]];[/color][/color]<br />
[color=#401082][color=#000000]	[[[/color][color=#b41ca4]self[/color][color=#000000] [/color]navigationController[color=#000000]] [/color]setToolbarHidden[color=#000000]:[/color][color=#b41ca4]NO[/color][color=#000000] [/color]animated[color=#000000]:[/color][color=#b41ca4]NO[/color][color=#000000]];[/color][/color]<br />
[color=#7134aa][color=#000000]	[/color][color=#b41ca4]self[/color][color=#000000].[/color]navigationController[color=#000000].[/color]navigationBar[color=#000000].[/color]barStyle[color=#000000]=[/color][color=#401082]UIBarStyleBlack[/color][color=#000000];[/color][/color]<br />
[color=#7134aa][color=#000000]	[/color][color=#b41ca4]self[/color][color=#000000].[/color]navigationController[color=#000000].[/color]toolbar[color=#000000].[/color]barStyle[color=#000000]=[/color][color=#401082]UIBarStyleBlack[/color][color=#000000];[/color][/color]<br />
<br />
[color=#7134aa][color=#000000]	[/color]UIBarButtonItem[color=#000000] *formButton = [[[/color]UIBarButtonItem[color=#000000] [/color][color=#401082]alloc[/color][color=#000000]][/color][/color]<br />
								   [color=#401082]initWithTitle[/color]:[color=#c72c25]@&quot;Form&quot;[/color]<br />
								   [color=#401082]style[/color]:[color=#401082]UIBarButtonItemStyleBordered[/color]<br />
								   [color=#401082]target[/color]:[color=#b41ca4]self[/color]<br />
								   [color=#401082]action[/color]:[color=#b41ca4]@selector[/color](accesForm1)];<br />
[color=#7134aa][color=#000000]	[/color][color=#b41ca4]self[/color][color=#000000].[/color]navigationItem[color=#000000].[/color]rightBarButtonItem[color=#000000]=formButton;[/color][/color]<br />
<br />
[color=#401082][color=#000000]	[/color][color=#b41ca4]if[/color][color=#000000]([[[/color][color=#b41ca4]self[/color][color=#000000] [/color][color=#38595d]path[/color][color=#000000]] [/color]isEqualToString[color=#000000]:[/color][color=#c72c25]@&quot;/&quot;[/color][color=#000000]])[/color][/color]<br />
	{<br />
		//méthode esseyé<br />
[color=#7134aa][color=#000000]		[/color][color=#b41ca4]self[/color][color=#000000].[/color]navigationController[color=#000000].[/color]navigationBar[color=#000000].[/color]backItem[color=#000000].[/color]hidesBackButton[color=#000000]=[/color][color=#b41ca4]YES[/color][color=#000000];[/color][/color]<br />
[color=#7134aa][color=#000000]	   //[/color][/color]<br />
<br />
	}[color=#b41ca4]else[/color]<br />
	{<br />
		[color=#7134aa]UIBarButtonItem[/color] *previousButton = [[[color=#7134aa]UIBarButtonItem[/color] [color=#401082]alloc[/color]]<br />
										   [color=#401082]initWithTitle[/color]:[color=#c72c25]@&quot;Preview&quot;[/color]<br />
										   [color=#401082]style[/color]:[color=#401082]UIBarButtonItemStyleBordered[/color]<br />
										   [color=#401082]target[/color]:[color=#b41ca4]self[/color]<br />
										   [color=#401082]action[/color]:[color=#b41ca4]@selector[/color](accesPrevious)];<br />
[color=#7134aa][color=#000000]		[/color][color=#b41ca4]self[/color][color=#000000].[/color]navigationItem[color=#000000].[/color]leftBarButtonItem[color=#000000]=previousButton;[/color][/color]<br />
	}<br />

Une idée ?