一个简单的检查iOS版本小于5(所有版本):

if([[[UIDevice currentDevice] systemVersion] integerValue] < 5){
        // do something
};

我知道现在回答这个问题已经太迟了。我不确定我的方法是否仍然适用于低iOS版本(< 5.0):

NSString *platform = [UIDevice currentDevice].model;

NSLog(@"[UIDevice currentDevice].model: %@",platform);
NSLog(@"[UIDevice currentDevice].description: %@",[UIDevice currentDevice].description);
NSLog(@"[UIDevice currentDevice].localizedModel: %@",[UIDevice currentDevice].localizedModel);
NSLog(@"[UIDevice currentDevice].name: %@",[UIDevice currentDevice].name);
NSLog(@"[UIDevice currentDevice].systemVersion: %@",[UIDevice currentDevice].systemVersion);
NSLog(@"[UIDevice currentDevice].systemName: %@",[UIDevice currentDevice].systemName);

你可以得到以下结果:

[UIDevice currentDevice].model: iPhone
[UIDevice currentDevice].description: <UIDevice: 0x1cd75c70>
[UIDevice currentDevice].localizedModel: iPhone
[UIDevice currentDevice].name: Someones-iPhone002
[UIDevice currentDevice].systemVersion: 6.1.3
[UIDevice currentDevice].systemName: iPhone OS

当前最好的版本，不需要在NSString中处理数字搜索是定义宏(查看原始答案:Check iPhone iOS版本)

这些宏确实存在于github中，参见:https://github.com/carlj/CJAMacros/blob/master/CJAMacros/CJAMacros.h

是这样的:

#define SYSTEM_VERSION_EQUAL_TO(v)                  ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] == NSOrderedSame)
#define SYSTEM_VERSION_GREATER_THAN(v)              ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] == NSOrderedDescending)
#define SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(v)  ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] != NSOrderedAscending)
#define SYSTEM_VERSION_LESS_THAN(v)                 ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] == NSOrderedAscending)
#define SYSTEM_VERSION_LESS_THAN_OR_EQUAL_TO(v)     ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] != NSOrderedDescending)

像这样使用它们:

if (SYSTEM_VERSION_LESS_THAN(@"5.0")) {
    // code here
}

if (SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(@"6.0")) {
    // code here
}

过时版本如下

获取操作系统版本:

[[UIDevice currentDevice] systemVersion]

返回字符串，可以通过转换为int/float

-[NSString floatValue]
-[NSString intValue]

像这样

这两个值(floatValue, intValue)将由于其类型而被剥离，5.0.1将变成5.0或5 (float或int)，为了精确比较，你必须将它分离为int数组 检查接受的答案在这里:检查iPhone iOS版本

NSString *ver = [[UIDevice currentDevice] systemVersion];
int ver_int = [ver intValue];
float ver_float = [ver floatValue];

像这样比较

NSLog(@"System Version is %@",[[UIDevice currentDevice] systemVersion]);
NSString *ver = [[UIDevice currentDevice] systemVersion];
float ver_float = [ver floatValue];
if (ver_float < 5.0) return false;

对于Swift 4.0语法

下面的例子只是检查设备是否为iOS11或更高版本。

let systemVersion = UIDevice.current.systemVersion
if systemVersion.cgFloatValue >= 11.0 {
    //"for ios 11"
  }
else{
   //"ios below 11")
  }

在MonoTouch:

要获得Major版本，请使用:

UIDevice.CurrentDevice.SystemVersion.Split('.')[0]

对于小版本使用:

UIDevice.CurrentDevice.SystemVersion.Split('.')[1]

[[UIDevice currentDevice] systemVersion]

一个简单的检查iOS版本小于5(所有版本):

if([[[UIDevice currentDevice] systemVersion] integerValue] < 5){
        // do something
};