使用swift Forget [[UIDevice currentDevice] systemVersion]和NSFoundationVersionNumber检查系统版本的新方法。

我们可以使用NSProcessInfo -isOperatingSystemAtLeastVersion

     import Foundation

     let yosemite = NSOperatingSystemVersion(majorVersion: 10, minorVersion: 10, patchVersion: 0)
     NSProcessInfo().isOperatingSystemAtLeastVersion(yosemite) // false

作为yasimturks解决方案的一种变体，我定义了一个函数和一些枚举值，而不是五个宏。我觉得它更优雅，但那是个人品味的问题。

用法:

if (systemVersion(LessThan, @"5.0")) ...

. h文件:

typedef enum {
  LessThan,
  LessOrEqual,
  Equal,
  GreaterOrEqual,
  GreaterThan,
  NotEqual
} Comparison;

BOOL systemVersion(Comparison test, NSString* version);

m文件:

BOOL systemVersion(Comparison test, NSString* version) {
  NSComparisonResult result = [[[UIDevice currentDevice] systemVersion] compare: version options: NSNumericSearch];
  switch (test) {
    case LessThan:       return result == NSOrderedAscending;
    case LessOrEqual:    return result != NSOrderedDescending;
    case Equal:          return result == NSOrderedSame;
    case GreaterOrEqual: return result != NSOrderedAscending;
    case GreaterThan:    return result == NSOrderedDescending;
    case NotEqual:       return result != NSOrderedSame;
  }
}

你应该在名称中添加应用程序的前缀，尤其是比较类型。

这两种常见的答案存在一些问题:

Comparing strings using NSNumericSearch sometimes has unintuitive results (the SYSTEM_VERSION_* macros all suffer from this): [@"10.0" compare:@"10" options:NSNumericSearch] // returns NSOrderedDescending instead of NSOrderedSame FIX: Normalize your strings first and then perform the comparisons. could be annoying trying to get both strings in identical formats. Using the foundation framework version symbols is not possible when checking future releases NSFoundationVersionNumber_iOS_6_1 // does not exist in iOS 5 SDK FIX: Perform two separate tests to ensure the symbol exists AND THEN compare symbols. However another here: The foundation framwork versions symbols are not unique to iOS versions. Multiple iOS releases can have the same framework version. 9.2 & 9.3 are both 1242.12 8.3 & 8.4 are both 1144.17 FIX: I believe this issue is unresolvable

为了解决这些问题，下面的方法将版本号字符串处理为以10000为基数的数字(每个主要/次要/补丁组件都是一个单独的数字)，并执行以十进制为基数的转换，以便使用整数运算符进行比较。

添加了另外两个方法，用于方便地比较iOS版本字符串，以及比较字符串与任意数量的组件。

+ (SInt64)integerFromVersionString:(NSString *)versionString withComponentCount:(NSUInteger)componentCount
{
    //
    // performs base conversion from a version string to a decimal value. the version string is interpreted as
    // a base-10000 number, where each component is an individual digit. this makes it simple to use integer
    // operations for comparing versions. for example (with componentCount = 4):
    //
    //   version "5.9.22.1" = 5*1000^3 + 9*1000^2 + 22*1000^1 + 1*1000^0 = 5000900220001
    //    and
    //   version "6.0.0.0" = 6*1000^3 + 0*1000^2 + 0*1000^1 + 0*1000^1 = 6000000000000
    //    and
    //   version "6" = 6*1000^3 + 0*1000^2 + 0*1000^1 + 0*1000^1 = 6000000000000
    //
    // then the integer comparisons hold true as you would expect:
    //
    //   "5.9.22.1" < "6.0.0.0" // true
    //   "6.0.0.0" == "6"       // true
    //

    static NSCharacterSet *nonDecimalDigitCharacter;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken,
        ^{  // don't allocate this charset every time the function is called
            nonDecimalDigitCharacter = [[NSCharacterSet decimalDigitCharacterSet] invertedSet];
        });

    SInt64 base    = 10000; // each component in the version string must be less than base
    SInt64 result  =     0;
    SInt64 power   =     0;

    // construct the decimal value left-to-right from the version string
    for (NSString *component in [versionString componentsSeparatedByString:@"."])
    {
        if (NSNotFound != [component rangeOfCharacterFromSet:nonDecimalDigitCharacter].location)
        {
            // one of the version components is not an integer, so bail out
            result = -1;
            break;
        }
        result += [component longLongValue] * (long long)pow((double)base, (double)(componentCount - ++power));
    }

    return result;
}

+ (SInt64)integerFromVersionString:(NSString *)versionString
{
    return [[self class] integerFromVersionString:versionString
                               withComponentCount:[[versionString componentsSeparatedByString:@"."] count]];
}

+ (SInt64)integerFromiOSVersionString:(NSString *)versionString
{
    // iOS uses 3-component version string
    return [[self class] integerFromVersionString:versionString
                               withComponentCount:3];
}

它支持许多版本标识符(通过4位数字，0-9999;可以支持任意数量的组件(Apple目前似乎使用3个组件，例如major.minor.patch)，但这可以使用componentCount参数显式指定。确保你的componentCount和base不会导致溢出，即确保2^63 >= base^componentCount!

使用的例子:

NSString *currentVersion = [[UIDevice currentDevice] systemVersion];
if ([Util integerFromiOSVersionString:currentVersion] >= [Util integerFromiOSVersionString:@"42"])
{
    NSLog(@"we are in some horrible distant future where iOS still exists");
}

#define _kisiOS7 ([[[UIDevice currentDevice] systemVersion] floatValue] >= 7.0)

if (_kisiOS7) {
            NSLog(@"iOS7 or greater")
} 
else {
           NSLog(@"Less than iOS7");
}

有7.0或6.0.3这样的版本，所以我们可以简单地将版本转换为数字进行比较。如果版本类似于7.0，只需追加另一个”。0”，然后取它的数值。

 int version;
 NSString* iosVersion=[[UIDevice currentDevice] systemVersion];
 NSArray* components=[iosVersion componentsSeparatedByString:@"."];
 if ([components count]==2) {
    iosVersion=[NSString stringWithFormat:@"%@.0",iosVersion];

 }
 iosVersion=[iosVersion stringByReplacingOccurrencesOfString:@"." withString:@""];
 version=[iosVersion integerValue];

为0

  if (version==600) {
    // Do something
  }

为7.0

 if (version==700) {
   // Do something
 }

if (floor(NSFoundationVersionNumber) > NSFoundationVersionNumber_iOS_6_1) {
        // Your code here
}

当然，其中NSFoundationVersionNumber_iOS_6_1必须更改为by适用于您要检查的iOS版本。我现在所写的内容在测试设备是否运行iOS7或之前的版本时可能会经常用到。