本问引自于：
关于iOS数据解析小数丢失精度的问题AFNetworking
目前发现
//出现BUG的条件是两位数或者一位数，且带两位小数，类型还必须是float//两位数：十位必须是7、8、9；个位数随意，一位数的个位数也必须是789//两位小数：第一位数随意；第二位数必须是
下面是正常请求。
NSURLSessionDataTask*task = [manager POST:httpStr parameters:secureDic progress:nilsuccess:^(NSURLSessionDataTask* _Nonnull task, id _Nullable responseObject) {
//请求回来打印responseObject
if(!isRedirect) {
[selfsaveCookies];
requestBlock(responseObject,nil);
}
} failure:^(NSURLSessionDataTask* _Nullable task, NSError* _Nonnull error) {
if(![DataRequest haveInternet]) {
NSDictionary*mesDic = @{@"mes":DataRequestNoInternetMessage};
NSDictionary*notWorkDic = @{@"message":mesDic};
requestBlock(notWorkDic,nil);
}else
requestBlock(dic,nil);
}];
打印结果如下，discount字段，服务器返回的是double，9.70，AFNetworking解析后就成了9.699999999999
后来查了下，发现是苹果的json解析会莫名其妙丢失精度
以下是测试结果
以下是测试结果
NSString *jsonStr = @"{\"9.70\":9.70, \"97.40\":97.40, \"80.40\":80.40, \"188.40\":188.40}";
NSLog(@"json:%@", jsonStr);
NSData *jsonData_ = [jsonStr dataUsingEncoding:NSUTF8StringEncoding];
NSError *jsonParsingError_ = nil;
NSDictionary *dic = [NSMutableDictionary dictionaryWithDictionary:[NSJSONSerialization JSONObjectWithData:jsonData_ options:0 error:&jsonParsingError_]];
NSLog(@"dic:%@", dic);
/*结果：dic:{
"188.40" = "188.4";
"80.40" = "80.40000000000001";
"9.70" = "9.699999999999999";
"97.40" = "97.40000000000001";
}*/
解决办法:
NSString *decimalNumberWithDouble(double conversionValue){
NSString *doubleString = [NSString stringWithFormat:@"%lf", conversionValue];
NSDecimalNumber *decNumber = [NSDecimalNumber decimalNumberWithString:doubleString];
return [decNumber stringValue];
