String NSString in iOS
Create a String object:
NSstring * str1 = @ "hello world ";
NSString * str = [[NSString alloc] initWithString: @ "hello world! "];
NSString * str_1 = [[NSString alloc] initwithuf8string: "hello world"]; // converts a C string to an OC string.
Int a = 123;
NSString * str_3 = [[NSString alloc] initWithFormat: @ "a = % d % s % @", a, "abcd", @ "efg"]; // initialize with a formatted string
// Concatenates strings and converts strings of C and OC.
NSString * str1 = [NSString stringWithString: @ "hello world"];
NSString * str2 = [NSString stringwithuf8string: "hello world"];
NSString * str3 = [NSString stringWithFormat: @ "% s", "hello world"];
NSstring * str1 = @ "hello ";
NSString * str = [[NSString alloc] initWithString: @ "hello world! "];
NSString * str_1 = [[NSString alloc] initwithuf8string: "hello world"]; // converts a C string to an OC string.
Int a = 123;
NSString * str_3 = [[NSString alloc] initWithFormat: @ "a = % d % s % @", a, "abcd", @ "efg"]; // initialize with a formatted string
String Conversion:
NSString * str = @ "hello ";
Const char * p = [str UTF8String]; converts an OC string to a C string.
Str = @ "123 ";
Int a = [str intValue]; // converts a numeric string to an integer.
[Str floatValue]; // converts a numeric string to the float type.
[Str doubleValue]; // converts a numeric string to the double type.
NSString * str = @ "hello ";
Const char * p = [str UTF8String]; converts an OC string to a C string.
Str = @ "123 ";
Int a = [str intValue]; // converts a numeric string to an integer.
[Str floatValue]; // converts a numeric string to the float type.
[Str doubleValue]; // converts a numeric string to the double type.
Common NSString:
NSLog (@ "% ld", [str1 length]); // evaluate the string length
NSLog (@ "% c", [str1 characterAtIndex: 1]); // obtain the characters in the string
BOOL ret = [str1 isEqualTo: str2]; // compares two strings for equality. If the two strings are equal, YES (1) is returned. If the two strings are not equal, NO (0) (bool yes (1) is returned) NO (0 ))
Long ret1 = [str1 compare: str2]; // compare the size of two strings. If str1 is greater than 1, return 1 equal. Return 0 Less than return-1
Long ret2 = [str1 caseInsensitiveCompare: str2]; // compare the string size case-insensitive
NSString * ptr = [str2 uppercaseString]; // converts all lowercase characters in the string to uppercase without changing the original string.
Ptr = [str1 lowercaseString]; // converts all uppercase characters in the string to lowercase without changing the original string
Ptr = [str3 capitalizedString]; // converts the first letter in the string to uppercase and lowercase letters.
NSString * str4 = @ "hello world ";
Nsange range = [str4 rangeOfString: @ "wr"]; // returns NSNotFound if no substring is found. Returns location and length.
If (range. location! = NSNotFound ){
NSLog (@ "% ld", range. location, range. length );
}
NSString * str5 = @ "helloworld ";
NSString * ptr1 = [str5 substringToIndex: 4]; // string extraction starts from subscript 0 to 4 excluding 4
NSString * ptr2 = [str5 substringFromIndex: 5]; // extracts data from subscript 5 to end of the string, including 5
Nsange range1 = {4, 3}; // structure Initialization
NSString * ptr3 = [str5 substringWithRange: range1]; // extract within the range specified
NSString * ptr4 = [str5 substringWithRange: NSMakeRange (4, 3)]; // NSMakeRange can generate a struct
NSString * str = @ "www.baidu.com ";
BOOL ret = [str hasPrefix: @ "www"]; // determines whether the string starts with a specified string.
NSString * str1 = @ "1.txt ";
BOOL ret1 = [str hasSuffix: @ ". txt"]; // determines whether the string ends with the specified string
NSMutableString variable string (dynamically increasing or decreasing) inherits all NSString methods that can be used
NSMutableString * str = [[NSMutableString alloc] initWithString: @ "hello"]; // converts an unchangeable string to a variable string
[Str insertString: @ "123" atIndex: 1]; // insert an NSString type string at the specified subscript (do not cross-border)
[Str appendString: @ "123"]; // append a string to the end of the string
[Str deleteCharactersInRange: NSMakeRange (0, 2)]; // Delete length characters from the specified subscript
[Str setString: @ "baidu"]; // you can modify a variable string to assign a value to it.
[Str replaceCharactersInRange: NSMakeRange (3, 1) withString: @ "ios"]; // Replace the length of the specified subscript with the specified string
