dict get

Subcommand of dict, used for getting a value out of a dictionary or nested set of dictionaries.

: dict get dict ?key …?

AMG: Here's a [dict getnull] command which returns empty string rather than raise an error when the requested element doesn't exist. This example uses {*} and [namespace ensemble]. It also takes advantage of the fact that the return value of [if] or a proc is the return value of the last command it executed, or empty string if it didn't execute anything.

proc ::tcl::dict::getnull {dictionary args} {
    if {[exists $dictionary {*}$args]} {
        get $dictionary {*}$args
    }
}
namespace ensemble configure dict -map\
    [dict replace [namespace ensemble configure dict -map]\
                  getnull ::tcl::dict::getnull]

Examples:

dict getnull {a b c {d e f g}} a    ;# b
dict getnull {a b c {d e f g}} c    ;# d e f g
dict getnull {a b c {d e f g}} c d  ;# e
dict getnull {a b c {d e f g}} c f  ;# g
dict getnull {a b c {d e f g}} h    ;# (empty string)
dict getnull {a b c {d e f g}} c h  ;# (empty string)

ufko Example kv:

proc kv {lst key} {
    set idx [lsearch $lst $key]
    if {$idx == -1} {
        return -1
    }
    incr idx
    return [lindex $lst $idx]
}

set L {id 100 name john}
puts [kv $L id]
set L {id 100 person {firstname Dave lastname Doe}}
puts [kv [kv $L person] lastname]