same day of last month ios

Question

Is there any way using NSCalender you can get same day of last month?

I am using a calender which shows user 1 month like the iPad calender when they click on the button I want to move to previous month but should select the same day as before.

I want to just do

[components setMonth:([components month] - 1)];

but this will create problems when I are moving from a month with 31 days to month with 30 days and selected day is 31st.

I was able to find examples for android but not iOS.

android example

Any help would be appreciated

Answer 1

Check out this link.

It's about adding one month, but you could probably do the same with subtracting.

Change

[dateComponents setMonth:1];

into

[dateComponents setMonth:-1];

Answer 2

Seems there is no obvious "right" answer and no "built-in" answer.

As Chris's "simple" idea may lead to invalid dates, you may have to handle the edge-cases.

Pseudocode to deal with day-month-year:

1. if month = December start with day-1-(year-1), else day-(month-1)-year [using dateComponents]
2. check if this a valid date (using NSDateFormatter like in this question
3. repeat subtracting one day until you reach a valid date

Another idea:

prevMonthDate = startDate;
Repeat
    prevMonthDate = prevMonthDate - 1 day
Until (Month(prevMonthDate) < Month(startDate) Or Year(prevMonthDate) < Year(startDate))
    And (Day(prevMonthDate) <= Day(startDate))

This requires working with NSDate and NSDateComponents, check out the Date and Time Programming Guide.