self.changeArray= [[NSArrayalloc]initWithObjects:@"0",@"1",@"2",@"3",@"4",@"5",@"6",@"7",@"8",@"9",@"a",@"b",@"c",@"d",@"e",@"f",@"g",@"h",@"i",@"j",@"k",@"l",@"m",@"n",@"o",@"p",@"q",@"r",@"s",@"t",@"u",@"v",@"w",@"x",@"y",@"z",nil];//存放多個數(shù)，以備隨機取,也可以加上大寫字母和其他符號
NSMutableString* getStr = [[NSMutableString alloc]initWithCapacity:5];
self.changeString= [[NSMutableString alloc]initWithCapacity:6];//申請內(nèi)存空間
for(inti =0; i<6; i++) {
NSInteger index =arc4random()%([self.changeArray count]-1);//循環(huán)六次黑毅，得到一個隨機數(shù)嚼摩，作為下標值取數(shù)組里面的數(shù)放到一個可變字符串里，在存放到自身定義的可變字符串
getStr =self.changeArray[index];
self.changeString= (NSMutableString*)[self.changeString stringByAppendingString:getStr];
}
NSLog(@"%@",self.changeString);
