ios 将 NSData 长度从字节转换为兆字节

convert NSData Length from bytes to megs

提问by HurkNburkS

I am trying to NSLogthe number of megs my NSDataobject is however currently all I can get is bytes by using

我正在尝试NSLog我的NSData对象的兆字节数，但是目前我只能通过使用获得字节数

NSLog(@"%u", myData.length);

So how would I change this NSLogstatement so I can see something like

那么我将如何更改此NSLog声明，以便我可以看到类似的内容

2.00 megs

2.00 兆

any help would be appreciated.

任何帮助，将不胜感激。

回答by Mick MacCallum

There are 1024 bytes in a kilobyte and 1024 kilobytes in a megabyte, so...

一千字节有 1024 字节，一兆字节有 1024 千字节，所以......

NSLog(@"File size is : %.2f MB",(float)myData.length/1024.0f/1024.0f);

Mind you, this is a simplistic approach that couldn't really properly accommodate for byte sizes below 1,048,576 bytes or above 1,073,741,823 bytes. For a more complete solution that can handle varying file sizes, see: ObjC/Cocoa class for converting size to human-readable string?

请注意，这是一种简单的方法，无法真正适应低于 1,048,576 字节或高于 1,073,741,823 字节的字节大小。有关可以处理不同文件大小的更完整的解决方案，请参阅：ObjC/Cocoa 类用于将大小转换为人类可读的字符串？

Or for OS X 10.8+ and iOS 6+

或用于 OS X 10.8+ 和 iOS 6+

NSLog(@"%@", [[NSByteCountFormatter new] stringFromByteCount:data.length]);

In Swift:

在斯威夫特：

print(ByteCountFormatter().string(fromByteCount: Int64(data.count)))

回答by Ber.to

For Swift 3, in Mb:

对于 Swift 3，以 Mb 为单位：

let countBytes = ByteCountFormatter()
countBytes.allowedUnits = [.useMB]
countBytes.countStyle = .file
let fileSize = countBytes.string(fromByteCount: Int64(dataToMeasure!.count))

print("File size: \(fileSize)")

回答by Imanou Petit

With Swift 5.1 and iOS 13, you can use one of the 5 following ways to solve your problem.

使用 Swift 5.1 和 iOS 13，您可以使用以下 5 种方法之一来解决您的问题。

---

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#1. Using ByteCountFormatter's string(fromByteCount:countStyle:)class method

#1. usingByteCountFormatter的string(fromByteCount:countStyle:)类方法

The following sample code shows how to implement string(fromByteCount:countStyle:)in order to print a file size by automaticallyconverting bytes to a more appropriate storage unit (e.g. megabytes):

以下示例代码显示了如何string(fromByteCount:countStyle:)通过自动将字节转换为更合适的存储单位（例如兆字节）来实现打印文件大小：

import Foundation

let url = Bundle.main.url(forResource: "image", withExtension: "png")!
let data = try! Data(contentsOf: url)

let byteCount = data.count
print(byteCount) // prints: 2636725

let displaySize = ByteCountFormatter.string(fromByteCount: Int64(byteCount), countStyle: .file)
print(displaySize) // prints: 2.6 MB

---

---

#2. Using ByteCountFormatter's string(fromByteCount:)method

#2. usingByteCountFormatter的string(fromByteCount:)方法

The following sample code shows how to implement ByteCountFormatter's string(fromByteCount:)in order to print a file size by manuallyconverting bytes to megabytes:

以下示例代码显示了如何通过手动将字节转换为兆字节来实现ByteCountFormatter'sstring(fromByteCount:)以打印文件大小：

import Foundation

let url = Bundle.main.url(forResource: "image", withExtension: "png")!
let data = try! Data(contentsOf: url)

let byteCount = data.count
print(byteCount) // prints: 2636725

let formatter = ByteCountFormatter()
formatter.allowedUnits = [.useMB]
formatter.countStyle = .file
let displaySize = formatter.string(fromByteCount: Int64(byteCount))
print(displaySize) // prints: 2.6 MB

---

---

#3. Using ByteCountFormatter's string(from:countStyle:)class method and Measurement

#3. usingByteCountFormatter的string(from:countStyle:)类方法和Measurement

The following sample code shows how to implement string(from:countStyle:)in order to print a file size by automaticallyconverting bytes to a more appropriate storage unit (e.g. megabytes):

以下示例代码显示了如何string(from:countStyle:)通过自动将字节转换为更合适的存储单位（例如兆字节）来实现打印文件大小：

import Foundation

let url = Bundle.main.url(forResource: "image", withExtension: "png")!
let data = try! Data(contentsOf: url)

let byteCount = data.count
print(byteCount) // prints: 2636725

let byteSize = Measurement(value: Double(byteCount), unit: UnitInformationStorage.bytes)
let displaySize = ByteCountFormatter.string(from: byteSize, countStyle: .file)
print(displaySize) // prints: 2.6 MB

---

---

#4. Using ByteCountFormatter's string(from:)method and Measurement

#4. usingByteCountFormatter的string(from:)方法和Measurement

The following sample code shows how to implement ByteCountFormatter's string(from:)and Measurementin order to print a file size by manuallyconverting bytes to megabytes:

以下示例代码显示了如何实现ByteCountFormatter'sstring(from:)并Measurement通过手动将字节转换为兆字节来打印文件大小：

import Foundation

let url = Bundle.main.url(forResource: "image", withExtension: "png")!
let data = try! Data(contentsOf: url)

let byteCount = data.count
print(byteCount) // prints: 2636725

let byteSize = Measurement(value: Double(byteCount), unit: UnitInformationStorage.bytes)
let formatter = ByteCountFormatter()
formatter.allowedUnits = [.useMB]
formatter.countStyle = .file
let displaySize = formatter.string(from: byteSize)
print(displaySize) // prints: 2.6 MB

---

---

#5. Using MeasurementFormatter's string(from:)method and Measurement

#5. usingMeasurementFormatter的string(from:)方法和Measurement

The following sample code shows how to implement Measurementand MeasurementFormatter's string(from:)in order to print a file size by manuallyconverting bytes to megabytes:

以下示例代码示出了如何实现Measurement和MeasurementFormatter的string(from:)，以便通过打印文件大小手动字节转换为兆字节：

import Foundation

let url = Bundle.main.url(forResource: "image", withExtension: "png")!
let data = try! Data(contentsOf: url)

let byteCount = data.count
print(byteCount) // prints: 2636725

let byteSize = Measurement(value: Double(byteCount), unit: UnitInformationStorage.bytes)
let convertedSize = byteSize.converted(to: .megabytes)
let formatter = MeasurementFormatter()
let displaySize = formatter.string(from: convertedSize)
print(displaySize) // prints: 2.637 MB