Modifying strings, Storing strings – Apple WebObjects 3.5 User Manual

Page 195

Commonly Used String Methods

195

Modifying Strings

Warning:

The following methods are not supported by NSString. They are

available only to NSMutableString objects.

– appendFormat:

Appends a constructed string to the receiver. Creates the new
string by using the

stringWithFormat:

method with the arguments

listed. For example, in the following code excerpt, if you assume
the variable

guestName

contains the string “Rena”, then

message

has

the resulting contents “Hi, Rena!”:

id message = [NSMutableString stringWithString:@"Hi"];
[message appendFormat:@", %@!", guestName];

– appendString:

Adds the characters of a speciﬁed string to the end of the receiver.
For example, the following statements create an
NSMutableString and append another string to its initial value:

id mutableString = [NSMutableString stringWithFormat:@"Hello "];
[mutableString appendString:@"world!"];

mutableString

has the resulting contents “Hello world!”.

– setString:

Replaces the characters of the receiver with those in a speciﬁed
string. For example, the following statement replaces the contents
of an NSMutableString with the empty string:

[mutableString setString:@""];

Storing Strings

– writeToFile:atomically:

Writes the string to a speciﬁed ﬁle, returning YES on success and
NO on failure. If YES is speciﬁed for

atomically:

, this method writes

the string to an auxiliary ﬁle and then renames the auxiliary ﬁle to
the speciﬁed path. In this way, it ensures that the contents of the
speciﬁed path do not become corrupted if the system crashes
during writing. The resulting ﬁle is suitable for use with

stringWithContentsOfFile:

. For example, the following code excerpt reads

the contents of an error log stored in a ﬁle, appends a new error to
the log, and saves the updated log to the same ﬁle:

id errorLog = [NSString stringWithContentsOfFile:errorPath];
id newErrorLog = [errorLog stringByAppendingFormat:@"%@: %@.\n",

timeStamp, @"premature end of file."];

[newErrorLog writeToFile:errorPath atomically:YES];