iOS 当请求到的数据是double类型，会失去精准度，并且去掉小数点后的0

首先请求到的数据都会变成字符串，先将字符串转化为double类型

double fdouble = [str doubleValue]；

然后再设置小数点后的位数

[NSString stringWithFormat:@"%.1f", fdouble];

重点：  提供一个NSSing的扩展，传入需要保留的小数位，返回字符串。并且去掉末尾的0.

#import <Foundation/Foundation.h>

@interface NSString (EliminateZero)

//   integer  必传
- (NSString *)eliminateZeroWithDouble:(NSInteger)integer;

@end

#import "NSString+EliminateZero.h"

@implementation NSString (EliminateZero)

- (NSString *)eliminateZeroWithDouble:(NSInteger)integer{

    NSString *str = [self copy];

    double fdouble = [str doubleValue];

    NSString *ftotal;
    switch (integer) {
        case :
            ftotal = [NSString stringWithFormat:@"%.1f", fdouble];
            break;
        case :
            ftotal = [NSString stringWithFormat:@"%.2f", fdouble];
            break;
        case :
            ftotal = [NSString stringWithFormat:@"%.3f", fdouble];
            break;
        case :
            ftotal = [NSString stringWithFormat:@"%.4f", fdouble];
            break;
        case :
            ftotal = [NSString stringWithFormat:@"%.5f", fdouble];
            break;
        default:
            break;
    }

    while ([ftotal hasSuffix:@""]) {
        ftotal = [ftotal substringToIndex:[ftotal length]-];
    }

    if ([ftotal hasSuffix:@"."]) {
        ftotal = [ftotal substringToIndex:[ftotal length]-];
    }

    return ftotal;

}

@end