我将练习将Swift库转换为Objective-C。
如何将其转换为Objective-C？
let formatter = NSDate.formatter(format: dateFormat)
我试过了：
NSDateFormatter *formatter = [NSDate formatterWithFormat : dateFormat];
还尝试了以下方法：
NSDateFormatter *formatter = [NSDate formatterWithFormat : dateFormat : [NSTimeZone localTimeZone] : [NSLocale currentLocale]];
还尝试了以下方法：
NSDateFormatter *formatter = [NSDate formatter : dateFormat : [NSTimeZone localTimeZone] : [NSLocale currentLocale]];
错误：不知道选择器“ formatterWithFormat：”或“ formatter :::”的类方法
更多内容：
+ (NSDateFormatter *) formatter : (NSString *) format : (NSTimeZone*) timeZone : (NSLocale *) locale {
format = DefaultFormat;
timeZone = [NSTimeZone localTimeZone];
locale = [NSLocale currentLocale];
NSString *hashKey = [NSString stringWithFormat:@"%lu%lu%lu", (unsigned long)format.hash, (unsigned long)timeZone.hash, (unsigned long)locale.hash];
NSMutableDictionary *formatters = [NSDate sharedDateFormatters];
NSDateFormatter *cachedDateFormatter = formatters[hashKey];
if (cachedDateFormatter != nil) {
return cachedDateFormatter;
}
else {
NSDateFormatter *formatter = [[NSDateFormatter alloc]init];
formatter.dateFormat = format;
formatter.timeZone = timeZone;
formatter.locale = locale;
formatters[hashKey] = formatter;
return formatter;
}
}
中间有一些随机文本，所以我可以添加更多代码...
+ (NSDateFormatter *)formatter:(NSDateFormatterStyle)dateStyle timeStyle:(NSDateFormatterStyle)timeStyle relativeDateFormatting:(BOOL)doesRelativeDateFormatting timeZone:(NSTimeZone *)timeZone locale:(NSLocale *)locale {
timeZone = [NSTimeZone localTimeZone];
locale = [NSLocale currentLocale];
NSString *hashKey = [NSString stringWithFormat:@"%lu%lu%lu%lu%lu", (unsigned long)dateStyle, (unsigned long)timeStyle, (unsigned long)doesRelativeDateFormatting, (unsigned long)timeZone.hash, (unsigned long)locale.hash];
NSMutableDictionary *formatters = [NSDate sharedDateFormatters];
NSDateFormatter *cachedDateFormatter = formatters[hashKey];
if (cachedDateFormatter != nil) {
return cachedDateFormatter;
}
else {
NSDateFormatter *formatter = [[NSDateFormatter alloc]init];
formatter.dateStyle = dateStyle;
formatter.timeStyle = timeStyle;
formatter.doesRelativeDateFormatting = doesRelativeDateFormatting;
formatter.timeZone = timeZone;
formatter.locale = locale;
formatters[hashKey] = formatter;
return formatter;
}
}
原始的Swift代码：
private class func formatter(format format:String = DefaultFormat, timeZone: NSTimeZone = NSTimeZone.localTimeZone(), locale: NSLocale = NSLocale.currentLocale()) -> NSDateFormatter {
let hashKey = "\(format.hashValue)\(timeZone.hashValue)\(locale.hashValue)"
var formatters = NSDate.sharedDateFormatters()
if let cachedDateFormatter = formatters[hashKey] {
return cachedDateFormatter
} else {
let formatter = NSDateFormatter()
formatter.dateFormat = format
formatter.timeZone = timeZone
formatter.locale = locale
formatters[hashKey] = formatter
return formatter
}
}
中间有一些随机文本，所以我可以添加更多代码...
private class func formatter(dateStyle dateStyle: NSDateFormatterStyle, timeStyle: NSDateFormatterStyle, doesRelativeDateFormatting: Bool, timeZone: NSTimeZone = NSTimeZone.localTimeZone(), locale: NSLocale = NSLocale.currentLocale()) -> NSDateFormatter {
var formatters = NSDate.sharedDateFormatters()
let hashKey = "\(dateStyle.hashValue)\(timeStyle.hashValue)\(doesRelativeDateFormatting.hashValue)\(timeZone.hashValue)\(locale.hashValue)"
if let cachedDateFormatter = formatters[hashKey] {
return cachedDateFormatter
} else {
let formatter = NSDateFormatter()
formatter.dateStyle = dateStyle
formatter.timeStyle = timeStyle
formatter.doesRelativeDateFormatting = doesRelativeDateFormatting
formatter.timeZone = timeZone
formatter.locale = locale
formatters[hashKey] = formatter
return formatter
}
}
根据所有更新，Objective-C代码和Swift代码之间的主要区别在于Swift函数提供了参数的默认值。这使您可以使用零个或多个参数来调用函数（在这种情况下）。
由于Objective-C不支持默认参数值，因此您需要为每个参数传递一个值。
方法：
+ (NSDateFormatter *) formatter : (NSString *) format : (NSTimeZone*) timeZone : (NSLocale *) locale {
}
需要称为：
[WhateverClassThisIs formatter:someFormat :someTimeZone :someLocale];
请注意丑陋的语法，因为您没有命名所有参数（就像我在上一个问题中显示的那样）。
您还需要删除在方法开始时添加的为这些参数分配值的行。
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