objective c - How to overwrite existing text file, then append to it -


i read settings hardware device , need write them text file, 1 one, 1 line. if file exists, savepanel asks if want overwrite it. answer yes, file gets appended to.

- (ibaction)savesettings:(id)sender  {    self.savesettings = true;    self.firstwrite = true;    nssavepanel *savetext    = [nssavepanel savepanel];    [savetext setnamefieldstringvalue:@"savedsettings.txt"];    [savetext setdirectoryurl:[nsurl fileurlwithpath:@"documents"]];    [savetext setshowstagfield:no];    nsinteger saveint    = [savetext runmodal];    if(saveint == nsmodalresponseok)    {      nsurl *pathurl = [savetext url];      self.pathname = [pathurl path];      [self appendtofile:@"general configuration\n"];      [self appendtofile:@"1\n"];      [self appendtofile:@"1\n"];      [self appendtofile:@"configuration axis 1\n"];      [self readmovedelayaxis1];    } }  - (bool)appendtofile:(nsstring *)strcontent; {   bool result = yes;   nsfilehandle* fh = [nsfilehandle filehandleforwritingatpath:self.pathname]; if ( !fh )  {   [[nsfilemanager defaultmanager] createfileatpath:self.pathname contents:nil attributes:nil];   fh = [nsfilehandle filehandleforwritingatpath:self.pathname]; } if ( !fh ) return no; @try {   [fh seektoendoffile];   self.firstwrite = false;   [fh writedata:[strcontent datausingencoding:nsutf8stringencoding]]; } @catch (nsexception * e) {     result = no; } [fh closefile]; return result; }

the amended code per answer below

- (ibaction)savesettings:(id)sender {     self.savesettings = true;     nssavepanel *savetext   = [nssavepanel savepanel];     [savetext setnamefieldstringvalue:@"savedsettings.txt"];     [savetext setdirectoryurl:[nsurl fileurlwithpath:@"documents"]];     [savetext setshowstagfield:no];     nsinteger saveint   = [savetext runmodal];     if(saveint == nsmodalresponseok)     {         nsurl *pathurl = [savetext url];         nsfilemanager *filemgr;         filemgr = [nsfilemanager defaultmanager];          if ([filemgr fileexistsatpath:[pathurl path]] == yes)         {             [filemgr removeitematpath:[pathurl path] error: null];         }         self.pathname = [pathurl path];         [self appendtofile:@"general configuration\n"];         [self appendtofile:@"1\n"];         [self appendtofile:@"1\n"];         [self appendtofile:@"configuration axis 1\n"];         [self readmovedelayaxis1];     } }

the nssavepanel ui asking user if file should overwritten, other nsopenpanel/nssavepanel situations returns selected url(s) application.

your code needs check if file exists , truncate if so, checking if file not exist , creating if so.

you can use methods such truncatefileatoffset:, functions such ftruncate(2), etc.

hth


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