objective c - NSString stringWithFormat and NSArray -

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• how create nsstring format string @“xxx=%@, yyy=%@” , nsarray of objects? 13 answers

i need method generating string format-string , it's arguments inside nsarray did't find working solution on stackoverflow. don't build nor throw exceptions (first, second).

so write solution , want share you.

@implementation nsstring (ax_nsstring)  + (instancetype)ax_stringwithformat:(nsstring *)format array:(nsarray *)arrayarguments {     nsmethodsignature *methodsignature = [self ax_generatesignatureforarguments:arrayarguments];     nsinvocation *invocation = [nsinvocation invocationwithmethodsignature:methodsignature];      [invocation settarget:self];     [invocation setselector:@selector(stringwithformat:)];      [invocation setargument:&format atindex:2];     (nsinteger = 0; < [arrayarguments count]; i++) {         id obj = arrayarguments[i];         [invocation setargument:(&obj) atindex:i+3];     }      [invocation invoke];      __autoreleasing nsstring *string;     [invocation getreturnvalue:&string];      return string; }  //https://developer.apple.com/library/mac/documentation/cocoa/conceptual/objcruntimeguide/articles/ocrttypeencodings.html + (nsmethodsignature *)ax_generatesignatureforarguments:(nsarray *)arguments {     nsinteger count = [arguments count];     nsinteger sizeptr = sizeof(void *);     nsinteger sumarginvoke = count + 3; //self + _cmd + (nsstring *)format     nsinteger offsetreturntype = sumarginvoke * sizeptr;      nsmutablestring *mstring = [[nsmutablestring alloc] init];     [mstring appendformat:@"@%zd@0:%zd", offsetreturntype, sizeptr];     (nsinteger = 2; < sumarginvoke; i++) {         [mstring appendformat:@"@%zd", sizeptr * i];     }     return [nsmethodsignature signaturewithobjctypes:[mstring utf8string]]; }  @end