OC : NSMeasurement (物理单位换算)

NSUnitAcceleration 加速度单位

苹果的解释是 Base unit - metersPerSecondSquared ，也就是 秒每平方米的意思（㎡/s），学过中学物理都知道这个事加速度的意思，NSUnitAcceleration提供了两个属性

@property (class, readonly, copy) NSUnitAcceleration *metersPerSecondSquared;@property (class, readonly, copy) NSUnitAcceleration *gravity;

从字面意思来看第一个是 秒每平方米 ， 第二个是重力加速度；
那么这东西干啥子用的了 ？ 我们打开Apple的API不难发现

NSMeasurementFormatter *formatter = [[NSMeasurementFormatter alloc] init];[formatter setUnitOptions:NSMeasurementFormatterUnitOptionsProvidedUnit];[formatter setLocale:[[NSLocale alloc] initWithLocaleIdentifier:@"zh"]];NSMeasurement *measurement1 = [[NSMeasurement alloc] initWithDoubleValue:12 unit:NSUnitAcceleration.metersPerSecondSquared];NSMeasurement *measurement2 = [[NSMeasurement alloc] initWithDoubleValue:12 unit:NSUnitAcceleration.gravity];NSLog(@"%@",[formatter stringFromMeasurement:measurement1]);  // 12米/秒²NSLog(@"%@",[formatter stringFromMeasurement:measurement2]);  // 12 G

NSMeasurementFormatter ： 把指定数字封装成 加速度的，然后按照一定的格式输出。

NSUnitAngle 几何角度单位

Base unit - degrees ， degrees 其实是度的意思，eg：这个三角形的角多少度
Apple提供了若干弧度单位如下

@property (class, readonly, copy) NSUnitAngle *degrees;//度(°)@property (class, readonly, copy) NSUnitAngle *arcMinutes;//分(ʹ)@property (class, readonly, copy) NSUnitAngle *arcSeconds;//秒(ʺ)@property (class, readonly, copy) NSUnitAngle *radians;//弧度(rad)@property (class, readonly, copy) NSUnitAngle *gradians;//百分度制（grad）,1G = 直角的1%@property (class, readonly, copy) NSUnitAngle *revolutions;//转(rev)

我们将90度转成对应的其他单位

NSMeasurement *measurement = [[NSMeasurement alloc] initWithDoubleValue:90 unit:NSUnitAngle.degrees];NSMeasurement *measurement1 = [measurement measurementByConvertingToUnit:NSUnitAngle.arcMinutes];NSMeasurement *measurement2 = [measurement measurementByConvertingToUnit:NSUnitAngle.arcSeconds];NSMeasurement *measurement3 = [measurement measurementByConvertingToUnit:NSUnitAngle.radians];NSMeasurement *measurement4 = [measurement measurementByConvertingToUnit:NSUnitAngle.gradians];NSMeasurement *measurement5 = [measurement measurementByConvertingToUnit:NSUnitAngle.revolutions];NSLog(@"%f",measurement1.doubleValue);  // 5399.892002NSLog(@"%f",measurement2.doubleValue);  // 323997.408021NSLog(@"%f",measurement3.doubleValue);  // 1.570796NSLog(@"%f",measurement4.doubleValue);  // 100.000000NSLog(@"%f",measurement5.doubleValue);  // 0.250000

其实我们不难看出这个NSMeasurement的使用方法，即先初始化一个数值对应单位，然后在通过这个单位转成另外一个单位并获取值，为神马90度转分秒之后不是整数了？
我觉得这种问题我在这里就不用解释了 90° == π/2 rad , 90° == 100grad ， 90° == 0.25rev

NSUnitArea 面积单位

Base unit - squareMeters ，基础单位平方米

@property (class, readonly, copy) NSUnitArea *squareMegameters;//平方表  Megameter兆米（=100万米） @property (class, readonly, copy) NSUnitArea *squareKilometers;//平方千米@property (class, readonly, copy) NSUnitArea *squareMeters;//平方米@property (class, readonly, copy) NSUnitArea *squareCentimeters;///平方厘米@property (class, readonly, copy) NSUnitArea *squareMillimeters;///平方毫米@property (class, readonly, copy) NSUnitArea *squareMicrometers;///平方微米@property (class, readonly, copy) NSUnitArea *squareNanometers;///平方纳米@property (class, readonly, copy) NSUnitArea *squareInches;///平方英寸@property (class, readonly, copy) NSUnitArea *squareFeet;///平方英尺@property (class, readonly, copy) NSUnitArea *squareYards;///平方码@property (class, readonly, copy) NSUnitArea *squareMiles;///平方英里@property (class, readonly, copy) NSUnitArea *acres;///英亩@property (class, readonly, copy) NSUnitArea *ares;///公亩（等于100平方米）@property (class, readonly, copy) NSUnitArea *hectares;///公顷

同样需要来一段代码验证码:

NSMeasurement *measurement = [[NSMeasurement alloc] initWithDoubleValue:100000 unit:NSUnitArea.squareMeters];NSMeasurement *measurement1 = [measurement measurementByConvertingToUnit:NSUnitArea.squareKilometers];NSMeasurement *measurement2 = [measurement measurementByConvertingToUnit:NSUnitArea.squareCentimeters];NSMeasurement *measurement3 = [measurement measurementByConvertingToUnit:NSUnitArea.squareFeet];NSMeasurement *measurement4 = [measurement measurementByConvertingToUnit:NSUnitArea.ares];NSMeasurement *measurement5 = [measurement measurementByConvertingToUnit:NSUnitArea.hectares];NSLog(@"%f",measurement1.doubleValue);  // 0.100000NSLog(@"%f",measurement2.doubleValue);  // 1000000000.000000NSLog(@"%f",measurement3.doubleValue);  // 1076391.505118NSLog(@"%f",measurement4.doubleValue);  // 1000.000000NSLog(@"%f",measurement5.doubleValue);  // 10.000000

NSUnitConcentrationMass 单元集中质量（密度）

Base unit - gramsPerLiter ，这个名字的确略显抽象，其实用我们物理的话来说就是 密度 ，简直就是坑爹，来张图

首先看下这个货给我们提供了神马

@property (class, readonly, copy) NSUnitConcentrationMass *gramsPerLiter; //克每升@property (class, readonly, copy) NSUnitConcentrationMass *milligramsPerDeciliter;//毫克每分升+ (NSUnitConcentrationMass *)millimolesPerLiterWithGramsPerMole:(double)gramsPerMole; // 毫摩尔每升克每摩尔

使用方法 ：

NSMeasurement *measurement1 = [[NSMeasurement alloc] initWithDoubleValue:7890 unit:NSUnitConcentrationMass.gramsPerLiter];NSMeasurement *measurement2 = [measurement1 measurementByConvertingToUnit:NSUnitConcentrationMass.milligramsPerDeciliter];NSLog(@"%f",measurement1.doubleValue);  // 7890.000000NSLog(@"%f",measurement2.doubleValue);  // 789000.000000

这个是两个单位之间的转换，那么这个货不老实，提供了一个类方法
来段代码

NSMeasurement *measurement1 = [[NSMeasurement alloc] initWithDoubleValue:100 unit:NSUnitConcentrationMass.gramsPerLiter];NSMeasurement *measurement2 = [[NSMeasurement alloc] initWithDoubleValue:1000000 unit:NSUnitConcentrationMass.milligramsPerDeciliter];NSMeasurement *measurement3 = [[NSMeasurement alloc] initWithDoubleValue:1 unit:[NSUnitConcentrationMass millimolesPerLiterWithGramsPerMole:1]];NSMeasurementFormatter *formatter = [[NSMeasurementFormatter alloc] init];[formatter setUnitOptions:NSMeasurementFormatterUnitOptionsProvidedUnit];[formatter setLocale:[[NSLocale alloc] initWithLocaleIdentifier:@"zh"]];NSLog(@"%@",[formatter stringFromMeasurement:measurement1]);  // 100 g/LNSLog(@"%@",[formatter stringFromMeasurement:measurement2]);  // 10,000 g/LNSLog(@"%@",[formatter stringFromMeasurement:measurement3]);  // 18 g/L

NSUnitDispersion 单位分散

Base unit - partsPerMillion ，百万分之几

@property (class, readonly, copy) NSUnitDispersion *partsPerMillion;//百万分之几

这个真是良心就一个属性，来段代码

NSMeasurement *measurement1 = [[NSMeasurement alloc] initWithDoubleValue:90 unit:NSUnitDispersion.partsPerMillion];NSMeasurementFormatter *formatter = [[NSMeasurementFormatter alloc] init];[formatter setUnitOptions:NSMeasurementFormatterUnitOptionsProvidedUnit];[formatter setLocale:[[NSLocale alloc] initWithLocaleIdentifier:@"zh"]];NSLog(@"%@",[formatter stringFromMeasurement:measurement1]);  // 90 ppm

NSUnitDuration 单位时间

Base unit - seconds 基础单位是秒

@property (class, readonly, copy) NSUnitDuration *seconds;//秒@property (class, readonly, copy) NSUnitDuration *minutes;//分@property (class, readonly, copy) NSUnitDuration *hours;//小时

这个应该是用的最多的一个转换工具了，因为时间运算我们经常会用到的，时分秒之间的相互转换

NSMeasurement *measurement = [[NSMeasurement alloc] initWithDoubleValue:1500 unit:NSUnitDuration.seconds];NSMeasurement *measurement1 = [measurement measurementByConvertingToUnit:NSUnitDuration.minutes];NSMeasurement *measurement2 = [measurement measurementByConvertingToUnit:NSUnitDuration.hours];NSLog(@"%f",measurement1.doubleValue);  // 25.000000NSLog(@"%f",measurement2.doubleValue);  // 0.416667

NSUnitElectricCharge 单位电荷

Base unit - coulombs 基础单位是库仑，先来看下提供的单位 ,然后来一个公式 1库仑＝1安培·1秒

@property (class, readonly, copy) NSUnitElectricCharge *coulombs;//库仑@property (class, readonly, copy) NSUnitElectricCharge *megaampereHours;//兆安小时@property (class, readonly, copy) NSUnitElectricCharge *kiloampereHours;//安培小时@property (class, readonly, copy) NSUnitElectricCharge *ampereHours;//安培小时@property (class, readonly, copy) NSUnitElectricCharge *milliampereHours;//毫安小时@property (class, readonly, copy) NSUnitElectricCharge *microampereHours;//微安小时

这个跟上面的基本类似，但是还是来段代码

NSMeasurement *measurement = [[NSMeasurement alloc] initWithDoubleValue:8000000000 unit:NSUnitElectricCharge.coulombs];NSMeasurement *measurement1 = [measurement measurementByConvertingToUnit:NSUnitElectricCharge.coulombs];NSMeasurement *measurement2 = [measurement measurementByConvertingToUnit:NSUnitElectricCharge.megaampereHours];NSLog(@"%f",measurement1.doubleValue);  // 8000000000.000000NSLog(@"%f",measurement2.doubleValue);  // 2.222222

NSUnitElectricCurrent 单位电流

Base unit - amperes 基本单位安培

@property (class, readonly, copy) NSUnitElectricCurrent *megaamperes;//兆安@property (class, readonly, copy) NSUnitElectricCurrent *kiloamperes;//千安@property (class, readonly, copy) NSUnitElectricCurrent *amperes;//安@property (class, readonly, copy) NSUnitElectricCurrent *milliamperes;//毫安@property (class, readonly, copy) NSUnitElectricCurrent *microamperes;//微安

这里来个公式吧

1 MA = 1000KA 1 KA = 1000A1 A = 1000 mA1mA = 1000 μANSMeasurement *measurement = [[NSMeasurement alloc] initWithDoubleValue:12 unit:NSUnitElectricCurrent.amperes];NSMeasurement *measurement1 = [measurement measurementByConvertingToUnit:NSUnitElectricCurrent.kiloamperes];NSMeasurement *measurement2 = [measurement measurementByConvertingToUnit:NSUnitElectricCurrent.milliamperes];NSLog(@"%f",measurement1.doubleValue);  // 0.012000NSLog(@"%f",measurement2.doubleValue);  // 12000.000000

NSUnitElectricCurrent 单位电位差（电压）

Base unit - volts ，伏特.

@property (class, readonly, copy) NSUnitElectricPotentialDifference *megavolts;//兆伏@property (class, readonly, copy) NSUnitElectricPotentialDifference *kilovolts;//千伏@property (class, readonly, copy) NSUnitElectricPotentialDifference *volts;//伏@property (class, readonly, copy) NSUnitElectricPotentialDifference *millivolts;//毫伏@property (class, readonly, copy) NSUnitElectricPotentialDifference *microvolts;//微伏

公式还是需要的

1kV=1000V 1V=1000mV1mV=1000μvNSMeasurement *measurement = [[NSMeasurement alloc] initWithDoubleValue:12 unit:NSUnitElectricPotentialDifference.volts];NSMeasurement *measurement1 = [measurement measurementByConvertingToUnit:NSUnitElectricPotentialDifference.kilovolts];NSMeasurement *measurement2 = [measurement measurementByConvertingToUnit:NSUnitElectricPotentialDifference.millivolts];NSLog(@"%f",measurement1.doubleValue);  // 0.012000NSLog(@"%f",measurement2.doubleValue);  // 12000.000000

NSUnitElectricResistance 单元电阻

Base unit - ohms ， 欧姆，简称欧
先复习下高中的公式 ， 欧姆的定义是一段电路的两端电压为1V，通过的电流为1A时，这段电路的电阻为1Ω

@property (class, readonly, copy) NSUnitElectricResistance *megaohms;//兆欧@property (class, readonly, copy) NSUnitElectricResistance *kiloohms;//千欧@property (class, readonly, copy) NSUnitElectricResistance *ohms;//欧@property (class, readonly, copy) NSUnitElectricResistance *milliohms;//毫欧@property (class, readonly, copy) NSUnitElectricResistance *microohms;//微欧

NSMeasurement *measurement = [[NSMeasurement alloc] initWithDoubleValue:12 unit:NSUnitElectricResistance.ohms];NSMeasurement *measurement1 = [measurement measurementByConvertingToUnit:NSUnitElectricResistance.kiloohms];NSMeasurement *measurement2 = [measurement measurementByConvertingToUnit:NSUnitElectricResistance.milliohms];NSLog(@"%f",measurement1.doubleValue);  // 0.012000NSLog(@"%f",measurement2.doubleValue);  // 12000.000000

NSUnitEnergy 单位能量

Base unit - joules 基础单位 焦耳

@property (class, readonly, copy) NSUnitEnergy *kilojoules;//千焦耳@property (class, readonly, copy) NSUnitEnergy *joules;//焦耳@property (class, readonly, copy) NSUnitEnergy *kilocalories;//千卡@property (class, readonly, copy) NSUnitEnergy *calories;//卡路里@property (class, readonly, copy) NSUnitEnergy *kilowattHours;//千瓦时

焦耳是能量单位，我们听到比较多的是卡路里，饮料里面有多少卡的能量；千瓦时也比较常见，电脑一小时耗电多少

NSMeasurement *measurement = [[NSMeasurement alloc] initWithDoubleValue:3600000000 unit:NSUnitEnergy.joules];NSMeasurement *measurement1 = [measurement measurementByConvertingToUnit:NSUnitEnergy.calories];NSMeasurement *measurement2 = [measurement measurementByConvertingToUnit:NSUnitEnergy.kilowattHours];NSLog(@"%f",measurement1.doubleValue);  // 860420650.095602NSLog(@"%f",measurement2.doubleValue);  // 1000.000000

NSUnitFrequency 单元频率

Base unit - hertz 频率就是赫兹，简称 赫

@property (class, readonly, copy) NSUnitFrequency *terahertz;//太赫@property (class, readonly, copy) NSUnitFrequency *gigahertz;//千兆赫@property (class, readonly, copy) NSUnitFrequency *megahertz;//兆赫@property (class, readonly, copy) NSUnitFrequency *kilohertz;//千赫@property (class, readonly, copy) NSUnitFrequency *hertz;//赫@property (class, readonly, copy) NSUnitFrequency *millihertz;//毫赫@property (class, readonly, copy) NSUnitFrequency *microhertz;//微赫@property (class, readonly, copy) NSUnitFrequency *nanohertz;//纳米赫

NSMeasurement *measurement = [[NSMeasurement alloc] initWithDoubleValue:72000 unit:NSUnitFrequency.hertz];NSMeasurement *measurement1 = [measurement measurementByConvertingToUnit:NSUnitFrequency.kilohertz];NSMeasurement *measurement2 = [measurement measurementByConvertingToUnit:NSUnitFrequency.millihertz];NSLog(@"%f",measurement1.doubleValue);  // 72.000000NSLog(@"%f",measurement2.doubleValue);  // 72000000.000000

NSUnitFuelEfficiency 单位燃料效率

Base unit - litersPer100Kilometers 每升100公里

@property (class, readonly, copy) NSUnitFuelEfficiency *litersPer100Kilometers;//每升100公里@property (class, readonly, copy) NSUnitFuelEfficiency *milesPerImperialGallon;//英制加仑英里数@property (class, readonly, copy) NSUnitFuelEfficiency *milesPerGallon;//英里每加仑

NSMeasurement *measurement = [[NSMeasurement alloc] initWithDoubleValue:16 unit:NSUnitFuelEfficiency.litersPer100Kilometers];NSMeasurement *measurement1 = [measurement measurementByConvertingToUnit:NSUnitFuelEfficiency.milesPerImperialGallon];NSMeasurement *measurement2 = [measurement measurementByConvertingToUnit:NSUnitFuelEfficiency.milesPerGallon];NSLog(@"%f",measurement1.doubleValue);  // 17.655062NSLog(@"%f",measurement2.doubleValue);  // 14.700938

NSUnitLength 单位长度

Base unit - meters 基础单位米

@property (class, readonly, copy) NSUnitLength *megameters;//兆米（米制长度单位，=100万米）@property (class, readonly, copy) NSUnitLength *kilometers;//千米@property (class, readonly, copy) NSUnitLength *hectometers;//百米@property (class, readonly, copy) NSUnitLength *decameters;//十米@property (class, readonly, copy) NSUnitLength *meters;//米@property (class, readonly, copy) NSUnitLength *decimeters;//分米@property (class, readonly, copy) NSUnitLength *centimeters;//厘米@property (class, readonly, copy) NSUnitLength *millimeters;//毫米@property (class, readonly, copy) NSUnitLength *micrometers;//微米@property (class, readonly, copy) NSUnitLength *nanometers;//纳米@property (class, readonly, copy) NSUnitLength *picometers;//皮米@property (class, readonly, copy) NSUnitLength *inches;//英寸@property (class, readonly, copy) NSUnitLength *feet;//英尺(=12 英寸或 30.48 厘米)@property (class, readonly, copy) NSUnitLength *yards;//码（等于3英尺或36英寸或0.9144米）@property (class, readonly, copy) NSUnitLength *miles;//英里@property (class, readonly, copy) NSUnitLength *scandinavianMiles;//斯堪的那维亚英里@property (class, readonly, copy) NSUnitLength *lightyears;//光年@property (class, readonly, copy) NSUnitLength *nauticalMiles;//海里@property (class, readonly, copy) NSUnitLength *fathoms;//英寻@property (class, readonly, copy) NSUnitLength *furlongs;//弗隆，浪（相当于0.2公里）@property (class, readonly, copy) NSUnitLength *astronomicalUnits;//天文单位@property (class, readonly, copy) NSUnitLength *parsecs;//秒差距

NSMeasurement *measurement = [[NSMeasurement alloc] initWithDoubleValue:240 unit:NSUnitLength.meters];NSMeasurement *measurement1 = [measurement measurementByConvertingToUnit:NSUnitLength.yards];NSMeasurement *measurement2 = [measurement measurementByConvertingToUnit:NSUnitLength.furlongs];NSLog(@"%f",measurement1.doubleValue);  // 262.467192NSLog(@"%f",measurement2.doubleValue);  // 1.19303

NSUnitIlluminance 单位照度

Base unit - lux ， 这货就一个属性,
勒克斯lux，法定符号lx)是照度(Illuminance)的单位。等于1流明(lumen)的光通量(Luminous flux)均匀照在1平方米表面上所产生的照度。适宜于阅读和缝纫等的照度约为60勒克斯

@property (class, readonly, copy) NSUnitIlluminance *lux;//勒克斯

NSMeasurement *measurement1 = [[NSMeasurement alloc] initWithDoubleValue:90 unit:NSUnitIlluminance.lux];NSMeasurementFormatter *formatter = [[NSMeasurementFormatter alloc] init];[formatter setUnitOptions:NSMeasurementFormatterUnitOptionsProvidedUnit];[formatter setLocale:[[NSLocale alloc] initWithLocaleIdentifier:@"zh"]];NSLog(@"%@",[formatter stringFromMeasurement:measurement1]);  // 90勒克斯

NSUnitMass 单位质量

Base unit - kilograms 基础单位千克

@property (class, readonly, copy) NSUnitMass *kilograms;//千克@property (class, readonly, copy) NSUnitMass *grams;//克@property (class, readonly, copy) NSUnitMass *decigrams;//分克@property (class, readonly, copy) NSUnitMass *centigrams;//厘克@property (class, readonly, copy) NSUnitMass *milligrams;//毫克@property (class, readonly, copy) NSUnitMass *micrograms;//微克@property (class, readonly, copy) NSUnitMass *nanograms;//毫微克@property (class, readonly, copy) NSUnitMass *picograms;//微微克@property (class, readonly, copy) NSUnitMass *ounces;//盎司@property (class, readonly, copy) NSUnitMass *poundsMass;//镑@property (class, readonly, copy) NSUnitMass *stones;//英石(重量单位,合14磅) @property (class, readonly, copy) NSUnitMass *metricTons;//吨@property (class, readonly, copy) NSUnitMass *shortTons;//短吨@property (class, readonly, copy) NSUnitMass *carats;//克拉@property (class, readonly, copy) NSUnitMass *ouncesTroy;//金衡盎司@property (class, readonly, copy) NSUnitMass *slugs;//斯勒格1slug=14.5939kg(质量单位)

NSMeasurement *measurement = [[NSMeasurement alloc] initWithDoubleValue:240 unit:NSUnitMass.kilograms];NSMeasurement *measurement1 = [measurement measurementByConvertingToUnit:NSUnitMass.ounces];NSMeasurement *measurement2 = [measurement measurementByConvertingToUnit:NSUnitMass.poundsMass];NSLog(@"%f",measurement1.doubleValue);  // 8465.757774NSLog(@"%f",measurement2.doubleValue);  // 529.109861

NSUnitPower 单位功率

Base unit - watts 瓦特 ，功率

@property (class, readonly, copy) NSUnitPower *terawatts;//兆兆瓦@property (class, readonly, copy) NSUnitPower *gigawatts;//千兆瓦@property (class, readonly, copy) NSUnitPower *megawatts;//兆瓦@property (class, readonly, copy) NSUnitPower *kilowatts;//千瓦@property (class, readonly, copy) NSUnitPower *watts;//瓦@property (class, readonly, copy) NSUnitPower *milliwatts;//毫瓦@property (class, readonly, copy) NSUnitPower *microwatts;//微瓦@property (class, readonly, copy) NSUnitPower *nanowatts;//纳瓦@property (class, readonly, copy) NSUnitPower *picowatts;//皮瓦@property (class, readonly, copy) NSUnitPower *femtowatts;//毫微微瓦@property (class, readonly, copy) NSUnitPower *horsepower;//马力

NSMeasurement *measurement = [[NSMeasurement alloc] initWithDoubleValue:7500 unit:NSUnitPower.watts];NSMeasurement *measurement1 = [measurement measurementByConvertingToUnit:NSUnitPower.horsepower];NSMeasurement *measurement2 = [measurement measurementByConvertingToUnit:NSUnitPower.kilowatts];NSLog(@"%f",measurement1.doubleValue);  // 10.057664NSLog(@"%f",measurement2.doubleValue);  // 7.500000

NSUnitPressure 单位压力（压强）

Base unit - newtonsPerMetersSquared (equivalent to 1 pascal) 牛顿每平方米 ，也就是压强

@property (class, readonly, copy) NSUnitPressure *newtonsPerMetersSquared;//牛每平方米@property (class, readonly, copy) NSUnitPressure *gigapascals;//吉帕@property (class, readonly, copy) NSUnitPressure *megapascals;//兆帕@property (class, readonly, copy) NSUnitPressure *kilopascals;//千帕@property (class, readonly, copy) NSUnitPressure *hectopascals;//百帕@property (class, readonly, copy) NSUnitPressure *inchesOfMercury;//英寸汞柱@property (class, readonly, copy) NSUnitPressure *bars;//巴@property (class, readonly, copy) NSUnitPressure *millibars;//毫巴@property (class, readonly, copy) NSUnitPressure *millimetersOfMercury;//毫米汞柱@property (class, readonly, copy) NSUnitPressure *poundsForcePerSquareInch;//磅力每平方英寸

NSMeasurement *measurement = [[NSMeasurement alloc] initWithDoubleValue:75 unit:NSUnitPressure.bars];NSMeasurement *measurement1 = [measurement measurementByConvertingToUnit:NSUnitPressure.millimetersOfMercury];NSMeasurement *measurement2 = [measurement measurementByConvertingToUnit:NSUnitPressure.poundsForcePerSquareInch];NSLog(@"%f",measurement1.doubleValue);  // 56254.781656NSLog(@"%f",measurement2.doubleValue);  // 1087.782606

NSUnitSpeed 单位速度

Base unit - metersPerSecond m/s

@property (class, readonly, copy) NSUnitSpeed *metersPerSecond;//米每秒@property (class, readonly, copy) NSUnitSpeed *kilometersPerHour;//公里每小时@property (class, readonly, copy) NSUnitSpeed *milesPerHour;//英里每小时@property (class, readonly, copy) NSUnitSpeed *knots;//节 轮船速度

NSMeasurement *measurement = [[NSMeasurement alloc] initWithDoubleValue:100 unit:NSUnitSpeed.metersPerSecond];NSMeasurement *measurement1 = [measurement measurementByConvertingToUnit:NSUnitSpeed.knots];NSMeasurement *measurement2 = [measurement measurementByConvertingToUnit:NSUnitSpeed.kilometersPerHour];NSLog(@"%f",measurement1.doubleValue);  // 194.384617NSLog(@"%f",measurement2.doubleValue);  // 359.999712

NSUnitTemperature 单位温度

Base unit - kelvin 开尔文

@property (class, readonly, copy) NSUnitTemperature *kelvin;//开氏温度@property (class, readonly, copy) NSUnitTemperature *celsius; //摄氏温度@property (class, readonly, copy) NSUnitTemperature *fahrenheit;//华氏温度

NSMeasurement *measurement = [[NSMeasurement alloc] initWithDoubleValue:100 unit:NSUnitTemperature.celsius];NSMeasurement *measurement1 = [measurement measurementByConvertingToUnit:NSUnitTemperature.kelvin];NSMeasurement *measurement2 = [measurement measurementByConvertingToUnit:NSUnitTemperature.fahrenheit];NSLog(@"%f",measurement1.doubleValue);  // 373.150000NSLog(@"%f",measurement2.doubleValue);  // 212.000000

NSUnitVolume 单位体积

Base unit - liters 升

@property (class, readonly, copy) NSUnitVolume *megaliters;//兆升@property (class, readonly, copy) NSUnitVolume *kiloliters;//千升@property (class, readonly, copy) NSUnitVolume *liters;//升@property (class, readonly, copy) NSUnitVolume *deciliters;//分升@property (class, readonly, copy) NSUnitVolume *centiliters;//厘升@property (class, readonly, copy) NSUnitVolume *milliliters;//毫升@property (class, readonly, copy) NSUnitVolume *cubicKilometers;//立方公里@property (class, readonly, copy) NSUnitVolume *cubicMeters;//立方米@property (class, readonly, copy) NSUnitVolume *cubicDecimeters;//立方分米@property (class, readonly, copy) NSUnitVolume *cubicCentimeters;//立方厘米@property (class, readonly, copy) NSUnitVolume *cubicMillimeters;//立方毫米@property (class, readonly, copy) NSUnitVolume *cubicInches;//立方英寸@property (class, readonly, copy) NSUnitVolume *cubicFeet;//立方英尺@property (class, readonly, copy) NSUnitVolume *cubicYards;//立方码@property (class, readonly, copy) NSUnitVolume *cubicMiles;//立方英里@property (class, readonly, copy) NSUnitVolume *acreFeet;//英亩英尺@property (class, readonly, copy) NSUnitVolume *bushels;//蒲式耳（2150.42立方英寸，或35.42升）@property (class, readonly, copy) NSUnitVolume *teaspoons;//茶匙@property (class, readonly, copy) NSUnitVolume *tablespoons;//汤匙@property (class, readonly, copy) NSUnitVolume *fluidOunces;//液盎司@property (class, readonly, copy) NSUnitVolume *cups;//杯@property (class, readonly, copy) NSUnitVolume *pints;//品脱@property (class, readonly, copy) NSUnitVolume *quarts;//夸脱@property (class, readonly, copy) NSUnitVolume *gallons;//加仑@property (class, readonly, copy) NSUnitVolume *imperialTeaspoons;//英制茶匙@property (class, readonly, copy) NSUnitVolume *imperialTablespoons;//一大汤匙@property (class, readonly, copy) NSUnitVolume *imperialFluidOunces;//英制液体盎司@property (class, readonly, copy) NSUnitVolume *imperialPints;//英制品脱@property (class, readonly, copy) NSUnitVolume *imperialQuarts;//英制夸脱@property (class, readonly, copy) NSUnitVolume *imperialGallons;//英制加仑@property (class, readonly, copy) NSUnitVolume *metricCups;//度量杯

NSMeasurement *measurement = [[NSMeasurement alloc] initWithDoubleValue:100 unit:NSUnitVolume.liters];NSMeasurement *measurement1 = [measurement measurementByConvertingToUnit:NSUnitVolume.teaspoons];NSMeasurement *measurement2 = [measurement measurementByConvertingToUnit:NSUnitVolume.gallons];NSLog(@"%f",measurement1.doubleValue);  // 20288.420181NSLog(@"%f",measurement2.doubleValue);  // 26.417218

原文章

http://blog.csdn.net/chmod_r_755/article/details/73850679