在alloc 生成的时候，都必须手动释放

-(void)Set_rankdictionary{

id data = [self readApplicationData:@"rank.plist"];

if (!data) {

_rankdictionary = [[NSMutableArray alloc] init];

}

else {

_rankdictionary =[[NSMutableArray alloc]initWithArray:data];

}

 

}