使用这个方法将NSString转换为NSdate:

-(NSDate *)getDateFromString:(NSString *)pstrDate
{
    NSDateFormatter* myFormatter = [[NSDateFormatter alloc] init];
    [myFormatter setDateFormat:@"dd/MM/yyyy"];
    NSDate* myDate = [myFormatter dateFromString:pstrDate];
    return myDate;
}

上面的例子不是简单地为Swift 3.0+编写的

更新- Swift 3.0+ -转换日期到字符串

let date = Date() // insert your date data here
var dateFormatter = DateFormatter()
dateFormatter.dateFormat = "yyyy-MM-dd" // add custom format if you'd like 
var dateString = dateFormatter.string(from: date)

字符串到日期

var dateFormatter = DateFormatter()
dateFormatter.format = "dd/MM/yyyy"

var dateFromString: Date? = dateFormatter.date(from: dateString) //pass string here

日期到字符串

 var dateFormatter = DateFormatter()
 dateFormatter.dateFormat = "dd-MM-yyyy"
 let newDate = dateFormatter.string(from: date) //pass Date here

Swift 4及后续版本

更新:2018

字符串到日期

var dateString = "02-03-2017"
var dateFormatter = DateFormatter()

// This is important - we set our input date format to match our input string
// if the format doesn't match you'll get nil from your string, so be careful
dateFormatter.dateFormat = "dd-MM-yyyy"

//`date(from:)` returns an optional so make sure you unwrap when using. 
var dateFromString: Date? = dateFormatter.date(from: dateString)

日期到字符串

var formatter = DateFormatter()
formatter.dateFormat = "dd-MM-yyyy"
guard let unwrappedDate = dateFromString else { return }

//Using the dateFromString variable from before. 
let stringDate: String = formatter.string(from: dateFromString)

斯威夫特3

更新:2017年7月20日

NSDate的字符串

var dateString = "02-03-2017"
var dateFormatter = DateFormatter()
// This is important - we set our input date format to match our input string
// if the format doesn't match you'll get nil from your string, so be careful
dateFormatter.dateFormat = "dd-MM-yyyy"
var dateFromString = dateFormatter.date(from: dateString)

NSDate到字符串

var formatter = DateFormatter()
formatter.dateFormat = "dd-MM-yyyy"
let stringDate: String = formatter.string(from: dateFromString)

斯威夫特

更新:2015年10月22日

NSDate的字符串

var dateString = "01-02-2010"
var dateFormatter = NSDateFormatter()
// this is imporant - we set our input date format to match our input string
dateFormatter.dateFormat = "dd-MM-yyyy"
// voila!
var dateFromString = dateFormatter.dateFromString(dateString)

NSDate到字符串

var formatter = NSDateFormatter()
formatter.dateFormat = "dd-MM-yyyy"
let stringDate: String = formatter.stringFromDate(NSDate())
println(stringDate)

objective - c

和陌生人约会

NSString *dateString = @"01-02-2010";
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"dd-MM-yyyy"];
NSDate *dateFromString = [dateFormatter dateFromString:dateString];

首次约会:

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"dd-MM-yyyy"];
NSString *stringDate = [dateFormatter stringFromDate:[NSDate date]];
NSLog(@"%@", stringDate);

使用这个方法将NSString转换为NSdate:

-(NSDate *)getDateFromString:(NSString *)pstrDate
{
    NSDateFormatter* myFormatter = [[NSDateFormatter alloc] init];
    [myFormatter setDateFormat:@"dd/MM/yyyy"];
    NSDate* myDate = [myFormatter dateFromString:pstrDate];
    return myDate;
}

// Convert string to date 

NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
[dateFormat setDateFormat:@"yyyyMMdd"];
NSDate *date = [dateFormat dateFromString:dateStr];  

// Convert Date to string

[dateFormat setDateFormat:@"EEEE MMMM d, YYYY"];
dateStr = [dateFormat stringFromDate:date];  
[dateFormat release];