NSDateFormatter，dateFromString返回nil

Question

添加了此代码

NSDateFormatter *df = [[NSDateFormatter alloc]init];
NSString *entry = @"March 28, 2012";       
[df setDateFormat:@"yyyy-MM-dd"];     
NSDate *date = [df dateFromString:entry]; 

日期返回nil值。我对输入日期字符串有疑问。是否可以将其转换为日期？

Answer 1

格式错误。请按以下步骤操作。

NSDateFormatter *df = [[NSDateFormatter alloc]init];
NSString *entry = @"March 28, 2012";       
[df setDateFormat:@"MMMM dd, yyyy"];     
NSDate *date = [df dateFromString:entry]; 

修改

[df setDateFormat:@"MMMM dd, yyyy HH:mm a"];     

Answer 2

您的日期格式字符串和日期值字符串不匹配。

无论

NSDateFormatter *df = [[NSDateFormatter alloc]init];
NSString *entry = @"2012-03-28";    //Changed this   
[df setDateFormat:@"yyyy-MM-dd"];   //Kept it as yours  
NSDate *date = [df dateFromString:entry]; 

OR

NSDateFormatter *df = [[NSDateFormatter alloc]init];
NSString *entry = @"March 28, 2012";   //Kept is as yours    
[df setDateFormat:@"MMMM dd, yyyy"];    //Changed it 
NSDate *date = [df dateFromString:entry];