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


Comments

Post a Comment

Popular posts from this blog

c++ - Difference between pre and post decrement in recursive function argument -

i have following sample code used pre-decrement void function(int c) { if(c == 0) { return; } else { cout << "dp" << c << endl; function(--c); cout << c << endl; return; } } this function give output input 4 : dp3 dp2 dp1 dp0 0 1 2 3 but when use post decrement void function(int c) { if(c == 0) { return; } else { cout << "dp" << c << endl; function(c--); cout << c << endl; return; } } output goes in infinite loop dp4 can explain me in detail why happens ? this happens because function(c--) called same value of c , when finishes c decremented. recursively called, hence called same value no chance of return , hit stack overflow error. assume this, int x = 1, y = 0; y = x++ result y == 1 , x == 2. if y = ++x , bot x , y 2.
Read more

javascript - How to insert selected radio button value into table cell -

i have 5 radio buttons <input type="radio" id="rating">1 <input type="radio" id="rating2">2 <input type="radio" id="rating3">3 <input type="radio" id="rating4">4 <input type="radio" id="rating5">5 i have 1 table <table id="mytabledata" border="1" style="width:100%"> <tr id="templaterow"> <th>ratings</th> </tr> </table> one add button <input type="button" id="add" value="add" onclick="addradiovalue()"> i've written code dynamically add rows table, when select radio button , click on add button, value of selected radio button should inserted new cell within table ratings. i able thing text box, i'm not able radio button. can me? your problems didn't have name set on radios , tryi
Read more

css - Transitioning Transforms in Safari look terrible/shaky/stuttering -

i have few functions based on scrolling user moves elements , down along page (imitating scroll effect.) in order make little smoother using transition: transform 0.7s cubic-bezier(0.49, 0.47, 0.63, 0.85); (with proper vender prefixing). the problem works great except in safari. there -webkit-transition: -webkit-transform 0.7s cubic-bezier(0.49, 0.47, 0.63, 0.85); causes animation jerk around , gives vibrating effect. have been reading on ages , have tried setting perspective property , backface properties no luck. is there way fix this/has seen this? , safari not allow transitioning transforms? any in understanding problem amazing. i found fiddle http://jsfiddle.net/3yfspjlt/ shows problem. if doesn't blink @ first keep scrolling , down. for curious code, more curious why bug happens in safari specific use case. (although of course trying find answer). js file getelementpositions: function(){ var de = document.documentelement; var windowhight = wind
Read more