Question

NSData * data;
NSFileHandle * file;

file = [NSFileHandle fileHandleForReadingAtPath: @"script.txt"]; //this is wrong, as I have to provide a full pathname, but disregard for now

[file seekToFileOffset: i]; //i not mentioned here, as this is only a snippet of code. Suffice to know that in the file it falls at the beginning of an integer I want to read

data = [file readDataOfLength: 5]; //5-digit integer that I want to read

现在我如何将数据转换为可以使用的int（即用于执行算术运算）？

Answer 1

由于您正在从文本文件中读取整数，因此可以将其转换为：

char buf[6];
[data getBytes:buf length:5];
buf[5] = '\0';
NSInteger res = atoi(buf);

这假定编码使用每个字符一个字节，这与您提供的代码段中[file readDataOfLength: 5]的调用一致。

如果未提前知道位数，您可以这样做：

char buf[11]; // Max 10 digits in a 32-bit number + 1 for null terminator
bzero(buf, 11);
[data getBytes:buf length:variableLength];
NSInteger res = atoi(buf);

Answer 2

更一般地说，您可以将此用于货币或科学记数法等，或者用于此处编码的int或浮点数...

NSString *string = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
NSNumberFormatter * format = [[NSNumberFormatter alloc] init];
[format setNumberStyle:NSNumberFormatterDecimalStyle];
NSNumber * myNumber = [format numberFromString:string];

Answer 3

这样做的一种方法是将数据转换为NSString，然后从中获取整数值：

// assuming UTF-8 encoding
NSString *temp = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
int val = [temp intValue];

参考文件： NSString

Answer 4

如果我这样做，假设script.txt包含纯文本，我会使用NSScanner：

NSError *error = nil;
NSString *fileString = [NSString stringWithContentsOfFile:scriptPath encoding:NSUTF8StringEncoding error:&error];
if (!fileString) { // Handle error }
NSScanner *scanner = [NSScanner scannerWithString:fileString];
[scanner setScanLocation:i];
int value = 0;
if (![scanner scanInt:&value]) { // Unable to scan integer from string }

// value should contain your integer here

Answer 5

NSData * dData;

const char * fData = [dData bytes];

Objective-C：将NSData转换为int或char

5 个答案: